Variation of the Complex Refractive Indices with Sb-addition in Ge-Sb-T Alloy and Their Wavelength Dependence

Abstract

With the increasing demand of the cost effective optical recording system, the optical media based on the phase-change phenomena have attracted an extensive research interest. One of the commonly used recording material for the phase-change optical disk is Ge-Sb-Te (GST) alloys which show a reversible phase transformation between the crystalline and the amorphous, thus the corresponding reflectivity change.[1,2] It has been reported that GST-alloys near to the stoichiometric compound are suitable for high speed application while other alloys like In-Sb-Te and Ag-In-Sh-Te are reported to be appropriate for low -speed applications.[3,4] The main purpose of this research is to study the feasibility of GST-alloys for the blue wavelength region for both high density recording and linear velocity applications. Variation of the complex refractive indices with Sb-addition in GST-alloy and their wavelength dependence were studied in the present research by using spectroscopic ellipsometry (SE) and atomic force microscopy (AFM). The reflectivity spectra of GST with different chemical compositions were calculated using these optical constants, and compared with the measured spectra.

Colloidal Ternary Telluride Quantum Dots for Tunable Phase Change Optics in the Visible and Near-Infrared

“…The complex refractive indices can then be used to calculate the reflectivity spectra ( R ) of Sn–Ge–Te thin films in the amorphous and crystalline phase with the following relationship: 50 …”

Simulation of waveguide integrated Ge2Sb2Te5-based tunable photodetector

“…To simulate the proposed structure, a new material is incorporated in the Lumerical tool with optical and electrical properties of GST material taken from the literature 32 , 53 , 68 – 70 as shown in Table 1. The complex refractive index real part of refractive index (n) and extinction coefficient (k) of a-GST and c-GST are considered to simulate the proposed structure 71 .…”

Analytic electrostatic model of amorphous-crystalline Ge2Sb2Te5 heterojunction

“…the positional dependence of the valence and conduction band edges on either side of the junction. As the band edge energies are related to the electrostatic potential, V(x), [15], only Poisson's Equation, given by equation (1), must be solved for V(x) across the heterojunction…”

“…Phase-change materials (PCMs) have several distinct properties. For instance, the prototypical PCM Ge 2 Sb 2 Te 5 (GST) can become 18% more reflective [1] and 2000 times more electrically resistive [2] as it transitions from the amorphous phase (a-GST) to the face-centred cubic crystalline phase (c-GST). Consequently, GST is utilised as the active material in a large range of devices, including optical disks and electronic phasechange random access memory (PCRAM), to take advantage of such unique properties.…”