Atomic Layer Deposition of Superconducting CuO Thin Films on Three-Dimensional Substrates

Aile Tamm,Helina Seemen,Valeriy Verchenko,Raivo Stern,Aivar Tarre

doi:10.3390/cryst10080650

Abstract

In previous decades, investigation of superconductors was aimed either at finding materials with higher critical temperatures or at discovering nontypical superconducting behavior. Here, we present the cupric (CuO) thin films, which were synthesized by atomic layer deposition by using a metal-organic precursor, copper (II)-bis-(-dimethylamino-2-propoxide), and ozone as an oxidizer. The deposition process was optimized by employing a quartz crystal monitoring, and the contact between the deposited films and planar and three-dimensional SiO2/Si substrates was examined by scanning electron microscopy with a focused ion beam module. Phase and elemental composition were analyzed by X-ray diffraction and X-ray fluorescence. Two-probe electrical resistivity measurements revealed a resistivity drop below the critical temperature of 4 K, which may indicate low-temperature superconductivity of the CuO thin films.

Highlights

Even since the first discovery of superconductivity [1], investigation of superconductors was aimed either at finding materials with higher critical temperatures Tc or, later, at discovering unconventional superconducting behavior, which significantly deviates from the conventionalBardeen-Cooper-Schrieffer model [2]
We report on atomic layer deposition of the CuO thin films by using the copper (II)-bis-(dimethylamino-2-propoxide) and ozone as precursors on planar and 3D stack type substrates
The cupric oxide films were grown in a low-pressure (200–260 Pa) flow-type in-house-built hot-wall atomic layer deposition (ALD) reactor (Tartu, Estonia)

Summary

Introduction

Even since the first discovery of superconductivity [1], investigation of superconductors was aimed either at finding materials with higher critical temperatures Tc or, later, at discovering unconventional superconducting behavior, which significantly deviates from the conventional. Several exotic superconductor-families based on copper, iron, hydrogen, carbon, and even nickel have been discovered and explored. More or less complex copper oxides, cuprates, are endowed with a unique combination of features that make them excellent magnetic model systems and/or good superconductors. The 3d9 electronic configuration of Cu2+ ensures the absence of the charge degrees of freedom. The low-energy physics of cuprates is driven by the magnetic degrees of freedom due to S = 1/2 spins localized on Cu2+

Methods

Results

Conclusion