Electrical Properties of MOS Capacitor with TiO 2 /SiO 2 Dielectric Layer
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ORIGINAL PAPER
Electrical Properties of MOS Capacitor with TiO2/SiO2 Dielectric Layer Saime Sebnem Cetin 1,2 & Halil Ibrahim Efkere 2,3 & Tunc Sertel 2,4 & Adem Tataroglu 1,2 & Suleyman Ozcelik 1,2 Received: 14 October 2019 / Accepted: 9 January 2020 # Springer Nature B.V. 2020
Abstract The TiO2/SiO2 film being the dielectric layer was grown on the n-Si wafer using radio frequency (RF) magnetron sputtering. Thus, the Au/TiO2/SiO2/n-Si metal-oxide-semiconductor (MOS) capacitor was fabricated with the forming of metal contacts. The optical properties of the oxide film were analyzed by Fourier transform infrared (FTIR) and Ultraviolet-visible (UV-Vis) spectroscopy. The electrical properties of the MOS capacitor were investigated using admittance (Y = G + iωC) measurements performed at various frequencies. The series resistance (Rs) parameter of the capacitor was derived from the conductance method. Keywords MOS capacitor . Dielectric . TiO2/SiO2 film . Admittance . Frequency dependence
1 Introduction The metal-oxide-semiconductor (MOS) structure or MOS capacitor can be thought of as a parallel-plate capacitor. The MOS structure has three parts as a top metal contact (gate)/ dielectric material/ semiconductor. The MOS structure is used in energy storage device applications due to the dielectric property of oxide [1–4]. While the ideal MOS structure includes no charge in the oxide and at the oxide-silicon interface, the real MOS always contains so-called oxide trapped charges, fixed charges, mobile ionic charges, and interface trap charges. These charges cause deviations in the capacitance-voltage (C-V) characteristics of MOS devices from the ideal curve shapes. Moreover, the parameters such as interface states (Nss) and series resistance (Rs) effect the electrical characteristics of MOS structure [5–8]. The capacitance of the MOS structure depends on the voltage that is
* Saime Sebnem Cetin [email protected] 1
Department of Physics, Faculty of Science, Gazi University, Teknikokullar, Ankara, Turkey
2
Photonics Application and Research Center, Gazi University, Teknikokullar, Ankara, Turkey
3
Department of Metallurgical and Materials Eng., Faculty of Technology, Gazi University, Teknikokullar, Ankara, Turkey
4
Department of Advanced Technologies, Graduate School of Natural and Applied Sciences, Gazi University, Teknikokullar, Ankara, Turkey
applied to the gate. C-V measurements are widely used to analyze the electrical characteristics of MOS capacitors. Titanium dioxide (TiO2) thin films have many applications such as solar cells [9], gas sensors [10, 11] dye-sensitized solar cells [12–14], and dielectrics [15]. TiO2 has three different crystal structures as rutile, anatase, and brookite, and these phases have different optical and electrical properties [16, 17]. Anatase and rutile structures are more preferred for technological applications. The optical bandgap values of rutile, anatase, and brookite TiO2 structures are approximately 3.0 eV, 3.4 eV, and 3.3 eV [18–22]. While TiO2 films have a rutile phase a
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