Electrical and optical properties of nickel-doped Ge2Sb2Te5 films produced by magnetron co-sputtering
Electrical and optical properties of nickel-doped Ge2Sb2Te5 films produced by magnetron co-sputtering
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DOI：
10.1117/12.2320843
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发表时间：
2018-09
期刊：
影响因子：
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通讯作者：
Pengfei Guo;Gary A. Sevison;J. Burrow;I. Agha;A. Sarangan
中科院分区：
文献类型：
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作者：
Pengfei Guo;Gary A. Sevison;J. Burrow;I. Agha;A. Sarangan
采用磁控共溅射系统制备了掺镍Ge2Sb2Te5(GST-Ni)薄膜。通过施加到GST和镍靶上的等离子体放电功率的比率以及进一步控制镍沉积速率的物理快门技术来调整薄膜中的镍含量。用能谱仪(EDS)确定了薄膜的掺杂浓度。四探针法测量结果表明，镍掺杂可使非晶态GST的电阻率降低近三个数量级。通过分析纯GST和GST-Ni在不同温度下的X射线衍射图，研究了掺杂对晶化行为的影响。为了研究镍掺杂对薄膜结构的影响，利用拉曼光谱对薄膜的结构进行了研究。此外，我们还用椭圆偏振法求出了未掺杂GST和GST-Ni薄膜的非晶态和晶态的光学常数。结果表明，在低掺杂浓度下，镍对材料的光学常数影响不大，但显著提高了材料的电导率。因此，掺镍GST是一种在较高开关速度、较低工作电压下设计光学器件的可行方法。
A magnetron co-sputtering system was used for producing nickel-doped Ge2Sb2Te5 (GST-Ni) thin films. The nickel content in the thin film was adjusted by the ratio of the plasma discharge power applied to the GST and nickel targets, as well as a physical shuttering technique to further control the nickel deposition rate. The doping concentration of the film was confirmed using Energy Dispersion Spectroscopy (EDS) technique. Results from a four-point probe measurement indicate that the nickel doping can reduce the resistivity of GST in the amorphous state by nearly three orders of magnitude. The dopant’s influence on crystallization behavior was studied by analyzing X-Ray Diffraction (XRD) patterns of the pure GST and GST-Ni at different annealing temperatures. To examine the structural changes due to the nickel dopant, the thin films were investigated with the aid of Raman scattering. Additionally, we extracted the optical constants for both the amorphous and crystalline states of undoped-GST and GST-Ni films by ellipsometry. The results indicate that at low doping concentrations nickel does not appreciably affect the optical constants, but dramatically improves the electrical conductivity. Therefore, nickel-doping of GST a viable method for designing optical devices for lower operating voltages at higher switching speeds.