Characterization of Nb2O5 Thin Films Coated by Sol-gel Method

Abstract

In this study, prepared niobium pentoxide (Nb2O5) solutions were aged for different times and under the same conditions. Nb2O5 thin films were deposited on the soda lime glass and silicon (Si) substrates under the same conditions by sol-gel spin coating method. The structural and optical properties and surface morphologies of the coated Nb2O5 thin films depending on the solution ageing were investigated by X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), UV-Vis spectrometer and atomic force mi-croscopy (AFM) analyzes, respectively. XRD results indicated that SG-1 sample (the film deposited using 1-day aged solution) had crystal structure and the particle size of the SG-1 sample was calculated as 46.12 nm. It was determined by SIMS analysis that the niobium (Nb) and oxygen (O) atomic species distributed homogeneously along the film depth. The SG-1 sample had 80% optical transmittance in the visible region and the energy band gap from the absorption spectrum was found to be about 3.65 eV. It was seen from the AFM surface images scanned in 5x5 µm2 area that SG-1 sample had smoother surface morphology with particle size value calculated as 70 nm. Also, it was seen from the AFM images that the RMS values increase as the solution ageing. The obtained results showed that the ageing time of Nb2O5 solution affects the structural, optical and surface morphology of the deposited films. It is suggested that the coated Nb2O5 thin films should be used as antireflective layer in crystal Si based solar cells.

Keywords

• Nb2O5,thin film,sol-gel,spin coating,ageing

Sol-jel Yöntemi ile Kaplanan Nb2O5 İnce Filmlerin Karakterizasyonu

Abstract

Bu çalışmada, hazırlanan niobyum pentoksit (Nb2O5) çözeltileri farklı sürelerde ve aynı koşullar altında yaşlandırıldı. Nb2O5 ince filmler, soda kireç cam ve silisyum alttaşlar üzerine aynı koşullar altında döndü-rerek kaplama cihazında sol-jel yöntemi ile kaplandı. Kaplanan Nb2O5 ince filmlerin yapısal ve optik özel-likleri ile yüzey morfolojilerinin çözeltinin yaşlanmasına olan bağımlılığı sırasıyla, X-ışını kırınımı (XRD), ikincil iyon kütle spektrometresi (SIMS), UV-Vis spektrofotometre ve atomik kuvvet mikroskobu (AFM) analizleri ile incelendi. XRD sonuçlarından, SG-1 (1 gün yaşlandırılan çözelti ile kaplanan film) numunesi-nin kristal yapıya sahip olduğu görüldü ve SG-1 numunesinin tanecik boyutu 46,12 nm olarak hesaplandı. SIMS analizi ile niobyum (Nb) ve oksijen (O) atomik türlerinin film derinliği boyunca homojen olarak dağıldığı tespit edildi. SG-1 numunesi görünür bölgede %80 civarında geçirgenliğe sahiptir ve soğurma spektrumundan elde edilen yasak enerji aralığı yaklaşık 3,65 eV olarak bulundu. Çözeltilerin yaşlandırılma süreleri artıkça, yansıtma değerleri kullanılarak hesaplanan kırılma indislerinin azaldığı görülmektir. AFM sonuçlarından, 5x5 µm2’lik alanda taranan yüzey görüntülerinden SG-1 numunesinin düzgün yüzey mor-folojisine ve 70 nm tanecik büyüklüğüne sahip olduğu görülmektedir. Ayrıca, AFM görüntülerinden çözelti yaşlandıkça RMS değerlerinin artığı görülmektedir. Elde edilen sonuçlar; Nb2O5 çözeltisinin yaşlandırılma süresinin kaplanan filmlerin yapısal, optik ve yüzey morfolojisini etkilediğini göstermektedir. Kaplanan Nb2O5 ince filmlerin Si temelli güneş hücrelerinde yansıma önleyici tabaka olarak kullanılması önerilmektedir.

Keywords

• Nb2O5,ince film,sol-jel,döndürerek kaplama,yaşlandırma,yaşlandırma

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