Indexed by: Journal paper

First Author: TONG HAO

Correspondence Author: 缪向水

Co-author: 周凌珺,余念念,yangzhe

Journal: Applied Physics Letters

Affiliation of Author(s): 华中科技大学

Discipline: Engineering

First-Level Discipline: Electronic Science And Technology

Document Type: J

Volume: 107

Issue: 8

Page Number: 082101

Key Words: Energy levels, Transport properties, Work functions, Heterostructures, Current-voltage characteristic, Atomic force microscopy, Partial differential equations, Metal oxides, Chemical elements

DOI number: 10.1063/1.4929369

Date of Publication: 4223-12-01

Abstract: The work function (WF) is of crucial importance to dominate the carrier transport properties of the Ge-Sb-Te based interfaces. In this letter, the electrostatic force microscopy is proposed to extract the WF of Ge2Sb2Te5 (GST) films with high spatial and energy resolution. The measured WF of as-deposited amorphous GST is 5.34 eV and decreases drastically after the amorphous GST is crystallized by annealing or laser illumination. A 512 x 512 array 2D-WF map is designed to study the WF spatial distribution and shows a good consistency. The WF contrast between a-GST and c-GST is ascribed to band modulation, especially the modification of electron affinity including the contribution of charges or dipoles. Then, the band alignments of GST/n-Si heterostructures are obtained based on the Anderson's rule. Due to the band modulation, the I-V characteristics of a-GST/Si heterojunction and c-GST/Si heterojunction are very different from each other. The quantitative relationship is calculated by solving the Poisson's equation, which agrees well with the I-V measurements. Our findings not only suggest a way to further understand the electrical transport properties of Ge-Sb-Te based interfaces but also provide a non-touch method to distinguish crystalline area from amorphous matrix with high spatial resolution. (C) 2015 AIP Publishing LLC.

Links to published journals: https://pubs.aip.org/aip/apl/article/107/8/082101/30931/Work-function-contrast-and-energy-band-modulation