Novel electrical transport properties of native Fe-Nb oxide layers leading to unilateral conductivity of a refractory metallic glass

A.S Trifonov,A.V Lubenchenko,S.V Ketov,S.V Taskaev,D.V Louzguine-Luzgin

doi:10.1016/j.heliyon.2019.e01424

Abstract

Fe-based metallic glasses (also called amorphous alloys) are known to have high hardness and high wear resistance. Here we study and present a Fe-Nb amorphous material with an unusual type of electrical conductivity behavior. The electrical transport properties of Fe-Nb oxide layers were studied by measuring local current-voltage characteristics by the atomic-force microscopy technique. At certain voltage levels the samples containing native oxides showed clearly asymmetrical conductivity relative to polarity of the applied potential. Fe-Nb metallic glassy surface oxide film growth process was monitored at ambient conditions. The growth rate keeps constant during the initial 2.5 hours. After that the growth rate drastically decreases and becomes almost zero while the final oxide thickness is 1.0–1.5 nm. The Fe-Nb film sample annealed for 15 minutes at 300 °C demonstrates several times larger oxide thickness and becomes an insulator. X-ray photoelectron spectroscopy was used to characterize the oxidation states in the surface amorphous oxides. This material can be readily applied as inexpensive nanoscale tunnel diode operating at the commonly utilized voltage of ±5 V.

Highlights

The thin films, representing practical interest, were first produced in middle of the past century
The Fe-Nb film sample annealed for 15 minutes at 300 C demonstrates several times larger oxide thickness
The electrical transport properties of Fe-Nb oxide layers were studied by measuring local current-voltage characteristics by the atomic-force microscopy technique

Summary

Introduction

The thin films, representing practical interest, were first produced in middle of the past century. The surface structure of the Ni62Nb38 (atomic percents) metallic glass was studied and found to consist of the atomic clusters [11, 12]. Successful application of metallic glasses in micro-electro-mechanical devices [13, 14] emphasizes the importance of their surface structure and properties. Thickness of a natural oxide on a metallic material is usually a few nanometers [16, 17], which becomes significant when a nano-mechanical element size of several tens or even hundreds of nanometer is used. In the present work we study the surface structure and properties of the Fe86Nb14 metallic glass film produced under conditions determined in [28] for the formation of smooth metallic films

Experimental

Results and discussion

Conclusion