Shekhawat Roopali, Pamuluri Haritha, Erkkara Madhavan Vinod, Ramesh K
Department of Physics, Indian Institute of Science, Bengaluru, 560012, India.
Sci Rep. 2021 Apr 7;11(1):7604. doi: 10.1038/s41598-021-87206-x.
GeTeSe (0 ≤ x ≤ 1.0) alloys have been prepared both in bulk and thin film forms to study the effect of selenium (Se) substitution for tellurium (Te) on the phase change properties. It is observed that with increasing Se substitution in GeTe, the structure transforms from rhombohdral structure to orthorhombic structure. Rietveld Refinement analysis support the phase transformation and show that the short and long bond lengths in crystalline GeTe decrease with increasing Se substitution but the rate of reduction of shorter bond length is more than the longer bond length. The GeTeSe thin films undergo amorphous to crystalline phase change when annealed at high temperatures. The transition temperature shows an increasing trend with the Se substitution. The contrast in electrical resistivity between the amorphous and crystalline states is 10 for GeTe, and with the Se substitution, the contrast increases considerably to 10 for GeTeSe. Devices fabricated with thin films show that the threshold current decreases with the Se substitution indicating a reduction in the power required for WRITE operation. The present study shows that the crystalline structure, resistance, bandgap, transition temperature and threshold voltage of GeTe can be effectively controlled and tuned by the substitution of Te by Se, which is conducive for phase change memory applications.
已经制备了块状和薄膜形式的GeTeSe（0 ≤ x ≤ 1.0）合金，以研究用硒（Se）替代碲（Te）对相变特性的影响。观察到，随着GeTe中Se替代量的增加，结构从菱形结构转变为正交结构。Rietveld精修分析支持这种相变，并表明晶体GeTe中的短键长和长键长随着Se替代量的增加而减小，但较短键长的减小速率大于较长键长。GeTeSe薄膜在高温退火时会经历非晶态到晶态的相变。转变温度随着Se替代量的增加呈上升趋势。GeTe的非晶态和晶态之间的电阻率对比度为10，随着Se替代，GeTeSe的对比度大幅增加到10。用薄膜制造的器件表明，阈值电流随着Se替代量的增加而降低，这表明写入操作所需的功率降低。本研究表明，通过用Se替代Te，可以有效地控制和调节GeTe的晶体结构、电阻、带隙、转变温度和阈值电压，这有利于相变存储器应用。
