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Öğe Wet chemical methods for producing mixing crystalline phase ZrO 2 thin film(Elsevier, 2016-07) Pakma, Osman; Özdemir, Cengiz; Kariper, İshak Afşin; Özaydın, Cihat; Güllü, ÖmerThe aim of the study is to develop a more economical and easier method for obtaining ZrO 2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO 2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO 2 /p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.Öğe Morphological, structural and optical characteristics of graphene oxide layers and metal/interlayer/semiconductor photovoltaic diode application(National Institute of Research and Development for Optoelectronics, 2018) Güllü, Ömer; Çankaya, MuratThis work describes the optical, morphological and structural characterizations of graphene oxide (GO) layers grown by drop casting and annealing process. UV-vis optical measurement shows that the values of direct and indirect optical gap energy of the GO film are 3.89 eV and 3.21 eV, respectively. The graphene oxide (GO) layer has been placed in the metal/ interlayer /semiconductor (MIS) diodes (total 17 devices) on p-Si wafers. The graphene oxide diodes give a better barrier height enhancement as compared with the conventional diodes. The value of homogeneous barrier height for Al/GO/p-Si MIS junctions was extracted as 0.74 eV. The diodes were also investigated under 300 watt light illumination for photovoltaic applications. Additionally, interfacial properties of the MIS diode with GO interlayer were determined. It has been seen that the capacitance of the device changes as a function of gate voltage and signal frequency from the capacitance-frequency measurements. It has also been reported that the interfacial trap charges reduce the capacitance with increasing frequency values.Öğe Barrier enhancement of Al/n-InP Schottky diodes by graphene oxide thin layer(Scientific Publishers, 2019) Güllü, Ömer; Çankaya, Murat; Rajagopal Reddy, VarraIn the present work, the surface morphology, structural and optical features of graphene oxide (GO) films are investigated. The Al/GO/n-InP MIS diode is formed by depositing GO layer on n-InP wafer for the barrier enhancement. Interfacial properties of the MIS diode with GO interlayer are extracted from current–voltage (I–V) measurement. The simple diode parameters such as barrier height and ideality factor are extracted from I–V plots, and the values are compared with those of conventional Al/n-InP MS contact. The value of barrier height (BH) for the Al/GO/n-InP contact is found as 0.85 eV. The BH value of 0.85 eV of the Al/GO/n-InP MIS structure is as high as around 100% compared to the value of 0.43 eV of the Al/n-InP reference contacts. We have showed that the value of 0.85 eV is one of the highest values presented for reference contacts with an interlayer.
