Phase change and optical band gap behavior of Ge-Te-Ga thin films prepared by thermal evaporation |
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Authors: | Guoxiang Wang Qiuhua Nie Xiang ShenFen Chen Jun LiWei Zhang Tiefeng XuShixun Dai |
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Affiliation: | a Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai Yutian Road 500#, Shanghai 200083, China b Laboratory of Infrared Material and Devices, Ningbo University, Ningbo 315211, China |
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Abstract: | The amorphous Ge11.4Te86.4Ga2.2 chalcogenide thin films were prepared by thermal evaporation onto chemically cleaned glass substrates. Properties measurements include X-ray diffraction (XRD), Scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), Four-point probe and VIS-NIR transmission spectra. The allowed indirect transition optical band gap and activation energy of samples were calculated according to the classical Tauc equation and Kissinger's equation, respectively. The results show that there is an amorphous-to-crystalline phase transition of Ge11.4Te86.4Ga2.2 thin film. The investigated film has high crystallization temperature (∼200 °C) and activation energy (2.48 eV), indicating the film has good amorphous stability. The sheet resistance of the crystalline state is ∼10 Ω/and the amorphous/crystalline resistance ratio is about 105. Besides, a wide optical band gap (0.653 eV) of Ge11.4Te86.4Ga2.2 is obtained, indicating that the material possesses a low threshold current from amorphous-to-crystalline state for phase-change memory application. |
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Keywords: | Thin film X-ray diffraction Electrical properties Optical properties |
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