INVESTIGATION OF CO EFFECT ON THE TEMPERATURE DEPENDENT OF THE

Öz

The Co effect on the temperature dependent electrical properties of ZnO thin films was examined. The ultrasonic spray pyrolysis technique were used for Co doped ZnO thin films on glass substrates prepared with cobalt at different concentrations. The effects of Co doping on the structural, optical and electrical properties of ZnO were investigated using with the results of x-ray diffraction (XRD), scanning electron microscope (SEM), EDX, optical transmittance measurements and electrical conductivity measurements. In the structure of Co doped ZnO samples, it is dominantly observed hexagonal wurtzite structure of ZnO. The effect of Co ions intercalated into ZnO crystal structure has been observed by examining the cubic phase of cobalt oxide in XRD difractograms and differences in the reflection peak (200) intensity. Phase changes of Co doped ZnO has been found to be controlled by the amount of Co. In the samples, Co threshold concentration value was determined by EDS analysis. The existence of Co in ZnO lattice has been proved by the Co2+characteristics as d-d transitions observed in the optical transmittance spectrum. The temperature dependent current of the samples are consistent with the electrical behavior of ZnO as the host material. All the films showed the single activation energy type behavior obtained from the dark conductivity measurement using lnk-1/T variation in the high temperature region. The single type of activation energy due to the increase of the Co content shows that a tendency to decrease after the critical value of Co molarity in the precursor solution

Anahtar Kelimeler

• ZnO, Co doping, electrical conductivity, ultrasonic spray pyrolysis technique

ZNO İNCE FİLMLERİN SICAKLIĞA BAĞLI ELEKTRİKSEL DAVRANIŞINDA CO ETKİSİNİN İNCELENMESİ

Öz

ZnO ince filmlerin sıcaklığa bağlı elektriksel özelliklerinde Co etkisi incelenmiştir. Cam alttaş üzerine, farklı Co molaritelerinde hazırlanan Co katkılanmış ZnO ince filmler için ultrasonik kimyasal püskürtme tekniği (UKP) kullanılmıştır. Co katkısının ZnO ince filmlerin yapısal, optiksel ve elektriksel özelliklerine etkisi x-ışını kırınım (XIK), taramalı elektron mikroskopu (SEM), EDS, optiksel geçirgenlik ve elektriksel iletkenlik ölçüm sonuçları ile değerlendirilmiştir. Co katkılı ZnO örneklerin yapısında, ZnO’e ait hekzagonal wurtzit yapının baskın olduğu gözlenmiştir. ZnO kristal yapısına giren Co iyonlarının etkisi, XIK desenlerinde kobalt oksite ait kübik fazın (200) yansıma pikindeki şiddet farkının ortaya çıkmasıyla gözlenmiştir. Co katkılı ZnO yapıdaki faz değişiminin, Co miktarı ile kontrol edildiği anlaşılmıştır. Örneklerdeki Co’ın eşik konsantrasyon değeri EDS analizi ile belirlenmiştir. ZnO örgüsü içindeki Co’ın varlığı, optik geçirgenlik spektrumlarındaki Co+2 iyonuna ait karakteristik d-d geçişlerinin gözlenmesiyle kanıtlanmıştır. Co katkılı ZnO örneklerin sıcaklığa bağlı akım değişimleri, ana malzeme olan ZnO’in davranışı ile uyumludur. Karanlık iletkenliklerinden elde edilen lnk-1/T grafiğinde, yüksek sıcaklık bölgesinde aktivasyon türü davranış gözlenmektedir. Artan Co miktarı ile tek tür aktivasyon enerjisinde gözlenen artış, Co’ın başlangıç ön çözelti molaritesindeki kritik değerden sonra azalma eğilimi göstermektedir

Anahtar Kelimeler

• ZnO, Co katkılama, elektriksel iletkenlik, ultrasonik kimyasal püskürtme tekniği

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