Theoretical and Experimental Comparison of the Properties of Hexagonal Wurtzite ZnO

Abstract

In this study, the optical and electronic properties of ZnO thin films were systematically investigated using both experimental methods and density functional theory (DFT) calculations. Structural optimizations and electrofilmnic property analyses were conducted using the PBE exchange–correlation functional. The results confirm that ZnO is a direct band gap semiconductor; however, the theoretically calculated band gap (0.87 eV) was significantly lower than the experimentally determined value (3.40 eV), consistent with the well-known underestimation problem of conventional DFT. This highlights the necessity of employing advanced computational methods such as hybrid functionals or GW corrections for precise band gap estimations. Despite the numerical discrepancy in band gap values, a strong spectral agreement was observed between the theoretical and experimental optical parameters, including the absorption coefficient, extinction coefficient, refractive index, and dielectric constants. Both methods indicated prominent optical transitions around 3.2–3.4 eV, especially in the UV region. Additionally, XRD and SEM analyses revealed high crystallinity and a homogeneous nanostructured morphology.

Keywords

• DFT
• Metal-oxide thin films
• Spin coating
• Sol-Gel

Hegzagonal Wurtzite ZnO'nun Özelliklerinin Teorik ve Deneysel Karşılaştırması

Abstract

Bu çalışmada, ZnO ince filmlerin optik ve elektronik özellikleri hem deneysel yöntemler hem de yoğunluk fonksiyonel teorisi (DFT) hesaplamaları kullanılarak sistematik olarak araştırılmıştır. Yapısal optimizasyonlar ve elektronik özellik analizleri, PBE değişim–korelasyon fonksiyonu kullanılarak gerçekleştirilmiştir. Sonuçlar, ZnO'nun doğrudan bant aralığına sahip bir yarıiletken olduğunu doğrulamaktadır; ancak teorik olarak hesaplanan bant aralığı değeri (0.87 eV), deneysel olarak belirlenen değerin (3.40 eV) oldukça altında kalmıştır. Bu durum, geleneksel DFT yöntemlerinin bant aralığını küçümseme eğilimine sahip olduğu yönündeki genel kabul ile uyumludur. Bu da, bant aralığının daha doğru tahmin edilebilmesi için hibrit fonksiyoneller veya GW düzeltmeleri gibi ileri düzey hesaplama yöntemlerinin gerekliliğini ortaya koymaktadır. Sayısal bant aralığı farkına rağmen, teorik ve deneysel optik parametreler arasında — soğurma katsayısı, sönümleme katsayısı, kırılma indisi ve dielektrik sabitleri dahil olmak üzere — güçlü bir spektral uyum gözlemlenmiştir. Her iki yöntem de özellikle UV bölgesinde, 3.2–3.4 eV civarında belirgin optik geçişleri göstermiştir. Ayrıca, XRD ve SEM analizleri, yüksek kristallilik ve homojen nanoyapılı bir morfolojiyi ortaya koymuştur.

Keywords

• DFT
• Metal-oksit ince filmler
• Spin kaplama
• Sol-Jel

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