Name: synthesis and characterization of high c-axis zno thin film by plasma enhanced chemical vapor deposition system and its uv photodetector application
Uploaded: 2015-10-03T14:00:00.000+00:00
Duration: 8 min 18 s
Description: Watch this Scientific Journal Video about Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application at JoVE.c

Questo lavoro è stato sostenuto finanziariamente della dal Ministero della Scienza e della Tecnologia e il National Science Council di Repubblica di Cina (nn contratto. NSC 101-2221-E-027-042 e 101-2622 NSC-E-027-003-CC2). DH Wei grazie alla nazionale di Taipei University of Technology (TAIPEI TECH) per il Dr. Shechtman Premio Award.

1. Preparazione del supporto e pulizia <ol><li> Tagliare 10 mm x 10 mm substrati di silicio da Si (100) wafer. </li><li> Tagliare 10 mm x 10 mm substrati di vetro. </li><li> Utilizzare ultrasuoni per pulire i substrati di silicio e vetro con acetone per 10 min, alcool per 10 minuti, e poi isopropanolo per 15 min. </li><li> Sciacquare i substrati con acqua deionizzata (DI) tre volte. </li><li> Blow-asciugare i supporti con una pistola di azoto. </li></ol> 2. DEZn preparazione e conservazione Nota: dietilzinco (C 2 H 5) 2 Zn, chiamato anche DEZn, è un composto altamente organozinco piroforica comprensivi di un centro di zinco legato a due gruppi etilici. Non lavorare mai da soli quando si usa DEZn. DEZn è molto tossico e sensibile per l&#39;ossigeno e l&#39;acqua, essere sicuri di non mettere il DEZn vicino all&#39;acqua. Indossare sempre maschere e occhiali di protezione; tutte le procedure devono essere eseguite nella cappa. Ancora più importante, DEZn non utilizzata deve be conservato in un ambiente 5 ° C. Nota: Per il primo utilizzo di DEZn, seguire passo 2. In caso contrario, avviare l&#39;esperimento dal punto 3. <ol><li> Utilizzare siringa per estrarre 30 ml DEZn dalla bottiglia e poi iniettare in un becher posto in un cilindro di acciaio. </li><li> Utilizzare un tubo di ferro galvanizzato per collegare il cilindro d&#39;acciaio con la camera di reazione. </li><li> Utilizzare pompa meccanica e valvola a sfera per pompare giù il cilindro di acciaio in ambiente sotto vuoto (a 6 Torr). Nota: DEZn severamente reagire con l&#39;ossigeno, deve essere mantenuto in ambiente sotto vuoto. </li><li> Conservare la DEZn non utilizzata in un ambiente di 5 ° C. </li></ol> 3. PECVD Camera Preparazione e sintesi di ZnO Thin Film Nota: Lo schema di plasma enhanced chemical vapour deposition è illustrato in Figura 1. <ol><li> Impostare la distanza di lavoro tra soffione elettrodo ed palco campione a 30 mm. </li> &lt;li&gt; Posizionare i substrati sulla scena campione di camera di reazione in posizione corretta in cui vi è un 3 cm di distanza dall&#39;ingresso DEZn. </li><li> Aprire la pompa rotativa e gradualmente aprire le saracinesche e valvola a farfalla. </li><li> Attendere che la pressione della camera del reattore sfondo è inferiore a 30 mTorr. </li><li> Chiudere il saracinesche e farfalla valvola, che si collega alla pompa rotativa. </li><li> Quindi aprire la pompa turbo e saracinesche relativi per raggiungere alto vuoto di 3 x 10 -6 Torr. </li><li> Dopo aver raggiunto la condizione di vuoto necessario, aprire il regolatore di calore e riscaldare la fase del campione alla temperatura di sintesi (200, 300, 400, 500, e 600 ° C per diversi parametri dell&#39;esperimento). </li><li> Quando la temperatura e la pressione raggiunge la condizione necessaria, chiudere la pompa turbo e quindi aprire il cancello e farfalla valvole valvola che collega alla pompa rotativa simultaneamente. </li><li> Quindi, aprire le valvole di aspirazione del gas e accendere l&#39;argon gcome regolatore di flusso contemporaneamente. </li><li> Il flusso del gas argon (0.167 ml / sec) nella camera. </li><li> Impostare la pressione della camera di 500 mTorr. </li><li> Accendere la rete RF (13.56 MHz) del generatore e di corrispondenza, quindi impostare la potenza RF di 100 W per l&#39;eliminazione dei campioni di superficie per 15 min. </li><li> Dopo aver terminato l&#39;epurazione dei campioni, accendere la potenza RF fino a 70 W. </li><li> Successivamente, accendere la valvola di controllo del gas di anidride carbonica e di ingresso del gas. </li><li> Flusso del biossido di carbonio (0,5 ml / sec) nella camera. </li><li> Impostare la pressione di esercizio di 6 Torr. </li><li> Dopo la pressione della camera raggiunge 6 Torr, l&#39;elevato flusso argon puro come gas di trasporto (0.167 ml / sec) per trasportare dietilzinco (DEZn) nella camera e valvola a sfera aperto collegato DEZn simultaneamente. Allo stesso tempo, iniziare la sintesi di film di ZnO. </li><li> Continuare la sintesi plasma di film di ZnO per 5 min. </li><li> Dopo i film di ZnO sono stati sintetizzati, seriatim spegnere il generatore RF, valvola a sfera, con il calorecontrollore e tutti controllori di flusso di gas con valvole di aspirazione gas. </li><li> Estrarre il campione quando la temperatura fase del campione si raffredda a temperatura ambiente. Nota: La velocità di raffreddamento è di circa 1,8 ° C / min. </li></ol> 4. Preparazione di interdigitata-come modello su As-sintetizzato ZnO film sottile Nota: Lo schema di processo di litografia è illustrato nella figura 3. <ol><li> Utilizzare una piastra calda per cuocere il campione come ZnO-sintetizzato a 150 ° C per 10 min. </li><li> Posizionare il campione sul dispositivo a induzione di rotazione, e quindi dispensare la soluzione liquida di fotoresist (S1813) con 100 microlitri sul campione ZnO. </li><li> Eseguire il dispositivo a induzione di rotazione a 800 giri al minuto per 10 secondi e poi accelerare a 3.000 rpm per 30 secondi per produrre uno strato uniforme sottile. </li><li> Morbido cuocere il campione ZnO photoresist rivestite a 105 ° C per 90 secondi. </li><li> Dopo il soft-cottura, utilizzare la luce UV per esporre il campione trou photoresist rivestitegh un fotomaschera per maschera allineatore. Il tempo di esposizione è di 2 secondi e la potenza è di 400 W. Nota:. Il modello di fotomaschera è progettato come interdigitati simile, che è 0,03 mm di larghezza e 4 mm di lunghezza (14 coppie) ed ha una distanza inter-elettrodo di 0,15 mm come illustrato nella figura 2 Vale la pena notare che il fotosensibile totale area è 84.32 mm 2 per il rivelatore. </li><li> Dopo la procedura di esposizione, usare una pinzetta per agganciare il campione, e poi immergono nella sviluppatore diluito (mescolare 50 ml di sviluppatore e 150 ml di acqua deionizzata) attraverso azioni di oscillare da un lato all&#39;altro per 35 s per ottenere il campione sviluppato. </li><li> Sciacquare il campione sviluppata con acqua deionizzata e asciugare con azoto. </li><li> Usate il microscopio ottico per controllare il motivo intatto. In caso contrario, usare acetone per rimuovere il photoresist e ripetere i passaggi 4,2-4,7 fino a quando è stato ottenuto il modello perfetto. </li><li> Duro cuocere il campione a 120 ° C per 20 min. </li></ol><ol><li> Utilizzare il sistema magnetron sputtering RF per depositare un sottile strato conduttivo Pt (100 nm) sulla parte superiore del campione sviluppato prima di procedere alla procedura di decollo chimica. </li><li> Impostare la distanza tra il target e il substrato a 13 mm. </li><li> Usare la pompa meccanica per raggiungere un vuoto di massima di 5 mTorr. </li><li> Quindi, utilizzare la pompa turbo per ottenere un alto vuoto di 7 x 10 -7 Torr. </li><li> Attendere fino a quando la camera raggiunge l&#39;alto vuoto, chiudere la pompa turbo e aprire la pompa meccanica successivamente. </li><li> Il flusso del gas argon a 0.3 ml / sec nella camera dal regolatore di flusso mas finché la pressione camera di raggiungere la pressione di esercizio di 100 mTorr. </li><li> Accendere la corrente continua (DC) di scarico alimentazione e impostare la corrente continua a 15 W per sputtering l&#39;elettrodo sottile pellicola di Pt sul campione per 25 minuti. </li><li> Dopo che lo strato dell&#39;elettrodo Pt è stato depositato da magnetron sputtMetodo rendo, togliere il campione dalla camera. </li><li> Immergere il campione nel liquido acetone per l&#39;industria chimica di processo decollo da ultrasuoni per rimuovere il photoresist. </li><li> Impostare il tempo di pulizia a 1 min per rimuovere completamente photoresist, e quindi ottenere l&#39;elettrodo interdigitata come Pt ​​sul film sottile ZnO. </li></ol> 6. processo RTA <ol><li> Mettere il campione Pt / ZnO come-fabbricato nel sistema RTA. </li><li> Usare la pompa meccanica e valvola a saracinesca per pompare giù la pressione della camera RTA a 20 mTorr. </li><li> Attendere che la pressione nella camera 20 raggiunge mTorr, flusso di gas argon a 0.3 ml / sec nella camera e impostare la pressione di esercizio di 5 Torr. </li><li> Successivamente, impostare la velocità di riscaldamento come 100 ° C / min. </li><li> Poi, ricuocere il campione a 450 ° C per 10 min. </li><li> Una volta ricotto, attendere fino a quando il campione si raffredda a RT, poi estrarre il campione. </li></ol>

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The authors declare that they have no competing financial interests.

Passaggi critici e modifiche Nella fase 1, i substrati devono essere puliti e passi 1,3-1,5 seguire per fare in modo che non ci sia grasso o contaminazioni organiche ed inorganiche sui substrati. Qualsiasi grasso o contaminazioni organici e inorganici sulla superficie del substrato ridurrà significativamente l&#39;adesione del film. Fase 2 è la procedura più importante prima del processo di preparazione del film ZnO. DEZn è molto tossico e reagisce violenteme...

ZnO è un wide-band-gap materiale semiconduttore funzionale promettente grazie alle sue proprietà uniche come l&#39;elevata stabilità chimica, a basso costo, atossicità, a bassa soglia di potenza per il pompaggio ottico, larga banda proibita diretta (3,37 eV) a temperatura ambiente e grandi eccitonico energia di ~ 60 meV 1-2 vincolante. Recentemente, film sottili ZnO sono stati impiegati in molti campi di applicazione contenenti ossido conduttivo (TCO) pellicole trasparenti, dispositivi emettitori di luce blu, transistori ad effetto di campo, e sensori di gas 3-6. D&#39;altra parte, ZnO è un materiale candidato per sostituire ossido di stagno indio (ITO) a causa di indio e stagno essendo raro e costoso. Inoltre, ZnO possiede alta trasmissione ottica nella regione di lunghezza d&#39;onda visibile e bassa resistività rispetto ITO film 7-8. Pertanto, fabbricazione, caratterizzazione e applicazione di ZnO è stato ampiamente riportato. Questo studio si concentra sulla sintesi (0002) ZnO film sottili di alta c -axis da un semplice und efficace metodo e la sua applicazione pratica verso una cellula fotoelettrica UV. Le recenti scoperte rapporto di ricerca indicano che la ZnO film sottile di alta qualità può essere sintetizzato mediante varie tecniche, come metodo sol-gel, magnetron sputtering a radiofrequenza, metallo organico deposizione di vapore chimico (MOCVD), e così via 9-14. Ogni tecnica ha i suoi vantaggi e svantaggi. Ad esempio, un vantaggio principale di deposizione sputtering è che i materiali bersaglio con molto elevato punto di fusione sono facilmente atomizzate sul substrato. Al contrario, il processo di sputtering è difficile combinare con un lift-off per strutturare il film. Nel nostro studio, il sistema potenziato a plasma chemical vapor deposition (PECVD) è stato impiegato per sintetizzare alta qualità c -axis film sottili ZnO. Bombardamento plasma è un fattore chiave nel processo di sintesi che può aumentare la densità di film sottile e migliorare la velocità di reazione di decomposizione di ioni 15. InInoltre, il tasso di crescita elevata e di grande superficie uniforme deposizione sono altri vantaggi distintivi per tecnica PECVD. Fatta eccezione per la tecnica di sintesi, la buona adesione sul substrato è un altro problema considerato. In molti studi, lo zaffiro c -Plane è stato ampiamente utilizzato come substrato per sintetizzare alta c -axis film sottili ZnO perché il ZnO e zaffiro hanno la stessa struttura reticolo esagonale. Tuttavia, la ZnO è stato sintetizzato su substrato di zaffiro esibendo morfologia superficiale ruvida e alte concentrazioni residue carrier (difetto relative) a causa delle grandi disadattati reticolari tra ZnO e c -Plane zaffiro (18%) orientate nella direzione 16 in piano. Rispetto al substrato di zaffiro, un wafer di Si è ampiamente usato un altro substrato per la sintesi ZnO. Wafer di Si sono stati ampiamente utilizzati nel settore dei semiconduttori; e quindi, la crescita di film sottili ZnO alta qualità su substrati di Si è molto importante e necessario. Purtroppo, la struttura cristallina e il coefficiente di espansione termica tra il ZnO e Si sono ovviamente diverse conseguente deterioramento della qualità di cristallo. Negli ultimi dieci anni, sono stati fatti notevoli sforzi per migliorare la qualità di film sottili su substrati di Si ZnO utilizzando vari metodi tra ZnO strati tampone 17, ricottura in atmosfera di gas diversi 18, e passivazione del substrato superficiale di Si 19. Il presente studio ha offerto con successo un metodo semplice ed efficace per sintetizzare alta c -axis ZnO film sottile su substrati di Si, senza strato tampone o pre-trattamento. I risultati dell&#39;esperimento è emerso che i film sottili ZnO sintetizzati sotto la temperatura di crescita ottimale mostrato il cristallo e buona qualità ottiche. La struttura cristallina, la composizione del plasma RF, morfologia superficiale e le proprietà ottiche di film sottili ZnO sono stati studiati mediante diffrazione di raggi X (XRD), spettroscopia di emissione ottica (OES), Field Emission scAnning microscopia elettronica (FE-SEM), e RT fotoluminescenza (PL) spettri rispettivamente. Inoltre, la trasmissione di film sottili ZnO è stato confermato anche e segnalato. Il film sottile ZnO come per sintesi servito come uno strato di rilevamento per l&#39;applicazione fotorivelatore UV è stata studiata anche in questo studio. Il rivelatore fotoelettrico UV ha grandi potenziali applicazioni nel monitoraggio UV, interruttore ottico, allarme fiamma, e il sistema di riscaldamento del missile 20-21. Ci sono molti tipi di fotorivelatori che sono state effettuate come modalità negativa intrinseco positivo (pin) e metallo-semiconduttore-metallo (MSM) strutture compreso il contatto ohmico e Schottky contatto. Ogni tipo ha i suoi vantaggi e svantaggi. Attualmente, le strutture fotorivelatori MSM hanno attirato l&#39;interesse intenso a causa della loro eccezionali prestazioni in responsività, l&#39;affidabilità e la risposta e il tempo di recupero 22-24. I risultati qui presentati dimostrano che la modalità di contatto ohmico MSM è stato impiegatofabbricare ZnO film sottile cellula fotoelettrica UV based. Tale tipo di fotorivelatore rivela in genere una buona responsività e affidabilità, indicando che l&#39;alta c -axis ZnO film sottile è uno strato di rilevamento adatto per fotorivelatore UV.

<table><tbody><tr><td>RF power supply</td><td>ADVANCED ENERGY</td><td>RFX-600</td><td></td></tr><tr><td>Butterfly valve</td><td>MKS</td><td>253B-1-40-1</td><td></td></tr><tr><td>Mass flow controller</td><td>PROTEC INSTRUMENTS</td><td>PC-540</td><td></td></tr><tr><td>Pressure controller</td><td>MKS</td><td>600 series&amp;nbsp;</td><td></td></tr><tr><td>Heater</td><td>UPGRADE INSTRUMENT CO.</td><td>UI-TC 3001</td><td></td></tr><tr><td>Sputter gun</td><td>AJA INTERNATIONAL</td><td>A320-HA</td><td></td></tr><tr><td>DEZn 1.5M</td><td>ACROS ORGANIC USA, New Jersey</td><td></td><td>also called Diethylzinc (C2H5)2Zn</td></tr><tr><td>Spin coater&amp;nbsp;</td><td>SWIENCO</td><td>PW - 490</td><td></td></tr><tr><td>I-V measurement</td><td>Keithley</td><td>Model: 2400</td><td></td></tr><tr><td>Photocondutive measurement&amp;nbsp;</td><td>Home-built</td><td></td><td></td></tr><tr><td>UV light sourse</td><td>Panasonic</td><td>ANUJ 6160</td><td></td></tr><tr><td>Mask aligner</td><td>Karl Suss</td><td>MJB4</td><td></td></tr><tr><td>Photoresist</td><td>Shipley a Rohm &amp;amp; Haas company</td><td>S1813</td><td></td></tr><tr><td>Developer</td><td>Shipley a Rohm &amp;amp; Haas company</td><td>MF319</td><td></td></tr><tr><td>Silicon wafer</td><td>E-Light Technology Inc</td><td>12/0801</td><td></td></tr><tr><td>Glass substrate</td><td>CORNING</td><td>1737</td><td>P-type / Boron</td></tr></tbody></table>

synthesis and characterization of high c-axis zno thin film by plasma enhanced chemical vapor deposition system and its uv photodetector application

In questo studio, l&#39;ossido di zinco (ZnO) film sottili con alta c -axis (0002) orientamento preferenziale sono stati correttamente ed efficacemente sintetizzato su silicio (Si) substrati con diverse temperature sintetizzati utilizzando plasma maggiore deposizione di vapore chimico sistema (PECVD). Gli effetti di diverse temperature di sintesi sulla struttura cristallina, morfologie di superficie e proprietà ottiche sono stati indagati. La diffrazione dei raggi X (XRD) modelli indicato che l&#39;intensità del picco (0002) diffrazione divenne più forte con l&#39;aumentare della temperatura sintetizzato fino 400 ° C. L&#39;intensità di diffrazione di (0002) di picco è diventato gradualmente più debole di accompagnamento con l&#39;apparenza di (10-10) di picco di diffrazione quando la temperatura sintetizzato fino all&#39;eccesso di 400 ° C. La RT fotoluminescenza (PL) spettri mostrato un forte nei pressi di banda-edge (NBE) emissione osservata a circa 375 nm e un trascurabile livello profondo (DL) emissione situato a circa 575 nm under alta c -axis ZnO film sottili. Campo microscopia elettronica a scansione emissione (FE-SEM) immagini hanno rivelato la superficie omogenea e con una distribuzione di piccole dimensioni del grano. I film sottili ZnO sono stati sintetizzati su substrati di vetro sotto gli stessi parametri di misurazione della trasmittanza. Ai fini dell&#39;applicazione ultravioletta (UV) fotorivelatore, il platino interdigitata (Pt) film sottile (spessore ~ ​​100 nm) fabbricato via convenzionale processo di litografia ottica e frequenza radio (RF) magnetron sputtering. Per raggiungere il contatto ohmico, il dispositivo è stato ricotto in circostanze argon a 450 o C per sistema rapido ricottura termica (RTA) per 10 min. Dopo le misurazioni sistematiche, la corrente-tensione (I - V) Curva di foto e risultati di risposta fotocorrente corrente e tempo-dipendente scuri esibito un buon responsività e affidabilità, indicando che l&#39;alta c -axis ZnO film sottile è uno strato di rilevamento adattoper l&#39;applicazione fotorivelatore UV.

Il ZnO (0002) film sottili con alta c -axis orientamento preferenziale sono stati sintetizzati con successo sui substrati di Si utilizzando il sistema PECVD. L&#39;anidride carbonica (CO 2) e la dietilzinco (DEZn) sono stati utilizzati come precursori di ossigeno e zinco, rispettivamente. La struttura cristallina di film sottili ZnO è stato caratterizzato da diffrazione dei raggi X (figura 4), ​​indicando che il film sottile ZnO sintetizzato a 400 ° C con la più for...

Watch this Scientific Journal Video about Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application at JoVE.c

Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

We offered a method to directly synthesize high c-axis (0002) ZnO thin film by plasma enhanced chemical vapor deposition. The as-synthesized ZnO thin film combined with Pt interdigitated electrode was used as sensing layer for ultraviolet photodetector, showing a high performance through a combination of its good responsivity and reliability.

Sintesi e caratterizzazione di alta c-asse ZnO film sottile da potenziato a plasma Chemical Vapor Deposition del sistema e la sua applicazione Rilevatori UV

In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto ...

synthesis-characterization-high-c-axis-zno-thin-film-plasma-enhanced

Universidad San Sebastian

Research

JoVE Journal

Engineering

15.2K Views.  National Taipei University of Technology (TAIPEI TECH). We offered a method to directly synthesize high c-axis (0002) ZnO thin film by plasma enhanced chemical vapor deposition. The as-synthesized ZnO thin film combined with Pt interdigitated electrode was used as sensing layer for ultraviolet photodetector, showing a high performance through a combination of its good responsivity and reliability.

Video: Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

Polycrystalline Silicon Thin-film Solar cells with Plasmonic-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To compensate for lower light absorption such physically thin devices have to incorporate light-trapping which increases their optical thickness. Light scattering by textured surfaces is a common technique but it cannot be universally applied to all solar cell technologies. Some cells, for example those made of evaporated silicon, are planar as produced and they require an alternative light-trapping means suitable for planar devices. Metal nanoparticles formed on planar silicon cell surface and capable of light scattering due to surface plasmon resonance is an effective approach.
The paper presents a fabrication procedure of evaporated polycrystalline silicon solar cells with plasmonic light-trapping and demonstrates how the cell quantum efficiency improves due to presence of metal nanoparticles.
To fabricate the cells a film consisting of alternative boron and phosphorous doped silicon layers is deposited on glass substrate by electron beam evaporation. An Initially amorphous film is crystallised and electronic defects are mitigated by annealing and hydrogen passivation. Metal grid contacts are applied to the layers of opposite polarity to extract electricity generated by the cell. Typically, such a ~2 &mu;m thick cell has a short-circuit current density (Jsc) of 14-16 mA/cm2, which can be increased up to 17-18 mA/cm2 (~25% higher) after application of a simple diffuse back reflector made of a white paint.
To implement plasmonic light-trapping a silver nanoparticle array is formed on the metallised cell silicon surface. A precursor silver film is deposited on the cell by thermal evaporation and annealed at 23&deg;C to form silver nanoparticles. Nanoparticle size and coverage, which affect plasmonic light-scattering, can be tuned for enhanced cell performance by varying the precursor film thickness and its annealing conditions. An optimised nanoparticle array alone results in cell Jsc enhancement of about 28%, similar to the effect of the diffuse reflector. The photocurrent can be further increased by coating the nanoparticles by a low refractive index dielectric, like MgF2, and applying the diffused reflector. The complete plasmonic cell structure comprises the polycrystalline silicon film, a silver nanoparticle array, a layer of MgF2, and a diffuse reflector. The Jsc for such cell is 21-23 mA/cm2, up to 45% higher than Jsc of the original cell without light-trapping or ~25% higher than Jsc for the cell with the diffuse reflector only.
Introduction
Light-trapping in silicon solar cells is commonly achieved via light scattering at textured interfaces. Scattered light travels through a cell at oblique angles for a longer distance and when such angles exceed the critical angle at the cell interfaces the light is permanently trapped in the cell by total internal reflection (Animation 1: Light-trapping). Although this scheme works well for most solar cells, there are developing technologies where ultra-thin Si layers are produced planar (e.g. layer-transfer technologies and epitaxial c-Si layers) 1 and or when such layers are not compatible with textures substrates (e.g. evaporated silicon) 2. For such originally planar Si layer alternative light trapping approaches, such as diffuse white paint reflector 3, silicon plasma texturing 4 or high refractive index nanoparticle reflector 5 have been suggested.
Metal nanoparticles can effectively scatter incident light into a higher refractive index material, like silicon, due to the surface plasmon resonance effect 6. They also can be easily formed on the planar silicon cell surface thus offering a light-trapping approach alternative to texturing. For a nanoparticle located at the air-silicon interface the scattered light fraction coupled into silicon exceeds 95% and a large faction of that light is scattered at angles above critical providing nearly ideal light-trapping condition (Animation 2: Plasmons on NP). The resonance can be tuned to the wavelength region, which is most important for a particular cell material and design, by varying the nanoparticle average size, surface coverage and local dielectric environment 6,7. Theoretical design principles of plasmonic nanoparticle solar cells have been suggested 8. In practice, Ag nanoparticle array is an ideal light-trapping partner for poly-Si thin-film solar cells because most of these design principle are naturally met. The simplest way of forming nanoparticles by thermal annealing of a thin precursor Ag film results in a random array with a relatively wide size and shape distribution, which is particularly suitable for light-trapping because such an array has a wide resonance peak, covering the wavelength range of 700-900 nm, important for poly-Si solar cell performance. The nanoparticle array can only be located on the rear poly-Si cell surface thus avoiding destructive interference between incident and scattered light which occurs for front-located nanoparticles 9. Moreover, poly-Si thin-film cells do not requires a passivating layer and the flat base-shaped nanoparticles (that naturally result from thermal annealing of a metal film) can be directly placed on silicon further increases plasmonic scattering efficiency due to surface plasmon-polariton resonance 10.
The cell with the plasmonic nanoparticle array as described above can have a photocurrent about 28% higher than the original cell. However, the array still transmits a significant amount of light which escapes through the rear of the cell and does not contribute into the current. This loss can be mitigated by adding a rear reflector to allow catching transmitted light and re-directing it back to the cell. Providing sufficient distance between the reflector and the nanoparticles (a few hundred nanometers) the reflected light will then experience one more plasmonic scattering event while passing through the nanoparticle array on re-entering the cell and the reflector itself can be made diffuse - both effects further facilitating light scattering and hence light-trapping. Importantly, the Ag nanoparticles have to be encapsulated with an inert and low refractive index dielectric, like MgF2 or SiO2, from the rear reflector to avoid mechanical and chemical damage 7. Low refractive index for this cladding layer is required to maintain a high coupling fraction into silicon and larger scattering angles, which are ensured by the high optical contrast between the media on both sides of the nanoparticle, silicon and dielectric 6. The photocurrent of the plasmonic cell with the diffuse rear reflector can be up to 45% higher than the current of the original cell or up to 25% higher than the current of an equivalent cell with the diffuse reflector only.

Polycrystalline silicon thin-film solar cells on glass are fabricated by deposition of boron and phosphorous doped silicon layers followed by crystallisation, defect passivation and metallisation. Plasmonic light-trapping is introduced by forming Ag nanoparticles on the silicon cell surface capped with a diffused reflector resulting in ~45% photocurrent enhancement.

Celle in silicio policristallino solari a film sottile con plasmoniche-enhanced Light-trapping

One of major approaches to cheaper solar cells is reducing the amount of semiconductor material used for their fabrication and making cells thinner. To ...

Ricerca

Ingegneria

Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Fabbricazione di nano-ingegneria trasparenti Ossidi Conducting da Pulsed Laser Deposition

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

Preparazione e utilizzo di fotocataliticamente attivo segmentata Ag | ZnO e coassiale TiO<sub&gt; 2</sub&gt;-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

Improved Heterojunction Quality in Cu2O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited Zn1-xMgxO

Atmospheric pressure spatial atomic layer deposition (AP-SALD) was used to deposit n-type ZnO and Zn1-xMgxO thin films onto p-type thermally oxidized Cu2O substrates outside vacuum at low temperature. The performance of photovoltaic devices featuring atmospherically fabricated ZnO/Cu2O heterojunction was dependent on the conditions of AP-SALD film deposition, namely, the substrate temperature and deposition time, as well as on the Cu2O substrate exposure to oxidizing agents prior to and during the ZnO deposition. Superficial Cu2O to CuO oxidation was identified as a limiting factor to heterojunction quality due to recombination at the ZnO/Cu2O interface. Optimization of AP-SALD conditions as well as keeping Cu2O away from air and moisture in order to minimize Cu2O surface oxidation led to improved device performance. A three-fold increase in the open-circuit voltage (up to 0.65 V) and a two-fold increase in the short-circuit current density produced solar cells with a record 2.2% power conversion efficiency (PCE). This PCE is the highest reported for a Zn1-xMgxO/Cu2O heterojunction formed outside vacuum, which highlights atmospheric pressure spatial ALD as a promising technique for inexpensive and scalable fabrication of Cu2O-based photovoltaics.

Improved Heterojunction Quality in Cu2O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited Zn1-xMgxO

Here we present a protocol for synthesizing Zn1-xMgxO/Cu2O heterojunctions in open-air at low temperature via atmospheric pressure spatial atomic layer deposition (AP-SALD) of Zn1-xMgxO on cuprous oxide. Such high quality conformal metal oxides can be grown on a variety of substrates including plastics by this cheap and scalable method.

Qualità Heterojunction migliorata in Cu<sub&gt; 2</sub&gt; O basati su celle solari attraverso l&#39;ottimizzazione della pressione atmosferica spaziale atomica strato depositato<br /&gt; Zn<sub&gt; 1-x</sub&gt; Mg<sub&gt; x</sub&gt; O

Atmospheric pressure spatial atomic layer deposition (AP-SALD) was used to deposit n-type ZnO and Zn1-xMgxO thin films onto p-type thermally oxidized Cu2O ...

Chimica

Synthesis of Hierarchical ZnO/CdSSe Heterostructure Nanotrees

A two-step chemical vapor deposition procedure is here employed to prepare tree-like hierarchical ZnO/CdSSe hetero-nanostructures. The structures are composed of CdSSe branches grown on ZnO nanowires that are vertically aligned on a transparent sapphire substrate. The morphology was measured via scanning electron microscopy. The crystal structure was determined by X-ray powder diffraction analysis. Both the ZnO stem and CdSSe branches have a predominantly wurtzite crystal structure. The mole ratio of S and Se in the CdSSe branches was measured by energy dispersive X-ray spectroscopy. The CdSSe branches result in strong visible light absorption. Photoluminescence (PL) spectroscopy showed that the stem and branches form a type-II heterojunction. PL lifetime measurements showed a decrease in the lifetime of emission from the trees when compared to emission from individual ZnO stems or CdSSe branches and indicate fast charge transfer between CdSSe and ZnO. The vertically aligned ZnO stems provide a direct electron transport pathway to the substrate and allow for efficient charge separation after photoexcitation by visible light. The combination of the abovementioned properties makes ZnO/CdSSe nanotrees promising candidates for applications in solar cells, photocatalysis, and opto-electronic devices.

Here, we prepare and characterize novel tree-like hierarchical ZnO/CdSSe nanostructures, where CdSSe branches are grown on vertically aligned ZnO nanowires. The resulting nanotrees are a potential material for solar energy conversion and other opto-electronic devices.

Sintesi di Hierarchical ZnO / CdSSe Heterostructure Nanotrees

A two-step chemical vapor deposition procedure is here employed to prepare tree-like hierarchical ZnO/CdSSe hetero-nanostructures. The structures are ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Aerosol-assisted Chemical Vapor Deposition di strutture in ossido di metallo: aste di ossido di zinco

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Well-aligned Vertically Oriented ZnO Nanorod Arrays and their Application in Inverted Small Molecule Solar Cells

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule (SMPV1) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM), by utilizing ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The inverted SMPV1:PC71BM solar cells with ZnO NRs that grew on both a sputtered and sol-gel processed AZO seed layer are fabricated. Compared with the AZO thin film prepared by the sol-gel method, the sputtered AZO thin film exhibits better crystallization and lower surface roughness, according to X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. The orientation of the ZnO NRs grown on a sputtered AZO seed layer shows better vertical alignment, which is beneficial for the deposition of the subsequent active layer, forming better surface morphologies. Generally, the surface morphology of the active layer mainly dominates the fill factor (FF) of the devices. Consequently, the well-aligned ZnO NRs can be used to improve the carrier collection of the active layer and to increase the FF of the solar cells. Moreover, as an anti-reflection structure, it can also be utilized to enhance the light harvesting of the absorption layer, with the power conversion efficiency (PCE) of solar cells reaching 6.01%, higher than the sol-gel based solar cells with an efficiency of 4.74%.

This manuscript describes how to design and fabricate efficient inverted SMPV1:PC71BM solar cells with ZnO nanorods (NRs) grown on a high quality Al-doped ZnO (AZO) seed layer. The well-aligned vertically oriented ZnO NRs exhibit high crystalline properties. The power conversion efficiency of solar cells can reach 6.01%.

Ben allineati verticalmente orientato ZnO Nanorod matrici e la loro applicazione in invertito piccola molecola solare celle

This manuscript describes how to design and fabricate efficient inverted solar cells, which are based on a two-dimensional conjugated small molecule ...

Fabrication of Schottky Diodes on Zn-polar BeMgZnO/ZnO Heterostructure Grown by Plasma-assisted Molecular Beam Epitaxy

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device applications. Zinc oxide (ZnO), a semiconductor with a wide bandgap (3.4 eV) and high electron saturation velocity has gained a great deal of attention as an attractive material for high speed devices. Efficient gate modulation, however, requires high-quality Schottky contacts on the barrier layer. In this article, we present our Schottky diode fabrication procedure on Zn-polar BeMgZnO/ZnO heterostructure with high density 2DEG which is achieved through strain modulation and incorporation of a few percent Be into the MgZnO-based barrier during growth by molecular beam epitaxy (MBE). To achieve high crystalline quality, nearly lattice-matched high-resistivity GaN templates grown by metal-organic chemical vapor deposition (MOCVD) are used as the substrate for the subsequent MBE growth of the oxide layers. To obtain the requisite Zn-polarity, careful surface treatment of GaN templates and control over the VI/II ratio during the growth of low temperature ZnO nucleation layer are utilized. Ti/Au electrodes serve as Ohmic contacts, and Ag electrodes deposited on the O2 plasma pretreated BeMgZnO surface are used for Schottky contacts.

Attainment of high-quality Schottky contacts is imperative for achieving efficient gate modulation in heterostructure field effect transistors (HFETs). We present the fabrication methodology and characteristics of Schottky diodes on Zn-polar BeMgZnO/ZnO heterostructures with high-density two dimensional electron gas (2DEG), grown by plasma-assisted molecular beam epitaxy on GaN templates.

Fabbricazione di diodi Schottky su Zn-polar eterostruttura BeMgZnO/ZnO cresciuto di epitassia da fasci molecolari assistita da Plasma

Heterostructure field effect transistors (HFETs) utilizing a two dimensional electron gas (2DEG) channel have a great potential for high speed device ...

The Effect of Anodization Parameters on the Aluminum Oxide Dielectric Layer of Thin-Film Transistors

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the dielectric layer of thin-film transistors (TFTs). Growth of aluminum-oxide layers from anodization of metallic aluminum films is greatly advantageous when compared to sophisticated processes such as atomic layer deposition (ALD) or deposition methods that demand relatively high temperatures (above 300 &#176;C) such as aqueous combustion or spray-pyrolysis. However, the electrical properties of the transistors are highly dependent on the presence of defects and localized states at the semiconductor/dielectric interface, which are strongly affected by the manufacturing parameters of the anodized dielectric layer. To determine how several fabrication parameters influence the device performance without performing all possible combination of factors, we used a reduced factorial analysis based on a Plackett-Burman design of experiments (DOE). The choice of this DOE permits the use of only 12 experimental runs of combinations of factors (instead of all 256 possibilities) to obtain the optimized device performance. The ranking of the factors by the effect on device responses such as the TFT mobility is possible by applying analysis of variance (ANOVA) to the obtained results.

Anodization parameters for growth of the aluminum-oxide dielectric layer of zinc-oxide thin-film transistors (TFTs) are varied to determine the effects on the electrical parameter responses. Analysis of variance (ANOVA) is applied to a Plackett-Burman design of experiments (DOE) to determine the manufacturing conditions that result in optimized device performance.

L'effetto dei parametri di anodizzazione sullo strato didielettrico dell'ossido di alluminio dei transistor a film sottile

Aluminum-oxide (Al2O3) is a low cost, easily processable and high dielectric constant insulating material that is particularly appropriate for use as the ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

Sintesi e caratterizzazione di alta c-asse ZnO film sottile da potenziato a plasma Chemical Vapor Deposition del sistema e la sua applicazione Rilevatori UV

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