A robust nitridation technique for fabrication of disordered superconducting TiN thin films featuring phase slip events

Sachin Yadav,M P Saravanan,Vinay Kaushik,Sangeeta Sahoo,V Ganesan,R P Aloysius

doi:10.1038/s41598-021-86819-6

Abstract

Disorder induced phase slip (PS) events appearing in the current voltage characteristics (IVCs) are reported for two-dimensional TiN thin films produced by a robust substrate mediated nitridation technique. Here, high temperature annealing of Ti/Si3N4 based metal/substrate assembly is the key to produce majority phase TiN accompanied by TiSi2 & elemental Si as minority phases. The method itself introduces different level of disorder intrinsically by tuning the amount of the non-superconducting minority phases that are controlled by annealing temperature (Ta) and the film thickness. The superconducting critical temperature (Tc) strongly depends on Ta and the maximum Tc obtained from the demonstrated technique is about 4.8 K for the thickness range ~ 12 nm and above. Besides, the dynamics of IVCs get modulated by the appearance of intermediated resistive steps for decreased Ta and the steps get more prominent for reduced thickness. Further, the deviation in the temperature dependent critical current (Ic) from the Ginzburg–Landau theoretical limit varies strongly with the thickness. Finally, the Tc, intermediate resistive steps in the IVCs and the depairing current are observed to alter in a similar fashion with Ta and the thickness indicating the robustness of the synthesis process to fabricate disordered nitride-based superconductor.

Highlights

Disorder induced phase slip (PS) events appearing in the current voltage characteristics (IVCs) are reported for two-dimensional titanium nitride (TiN) thin films produced by a robust substrate mediated nitridation technique
We have investigated the effects of Ta and film thickness on the temperature dependent critical current (Ic) by using Ginzburg–Landau (GL) theory[32] and we have found that the Ic and the phase slip lines (PSLs) vary in a similar fashion with Ta and the film thickness
The highest Tc appears for Ta = 820 °C, whereas, we do not observe any transition down to 2 K for the sample annealed at 650 °C

Summary

Introduction

Disorder induced phase slip (PS) events appearing in the current voltage characteristics (IVCs) are reported for two-dimensional TiN thin films produced by a robust substrate mediated nitridation technique. We demonstrate that by tuning the disorder the superconducting-to-normal state transition in the measured IVCs changes from a single step transition to a transition embedded with multiple steps featuring the formation of PSLs. The tuning of disorder level in TiN films has been achieved by adopting a novel substrate mediated nitridation technique[18,19,20], which employs high temperature annealing of Ti/Si3N4 based metal/. A fine tuning of nitrogen concentration is needed to achieve the stoichiometric highly crystalline fcc TiN known to possess higher superconducting critical temperature (Tc) By using this substrate mediated nitridation technique, we have produced 3–20 nm thick TiN films with Tc ranging from 3.0 to 4.8 K, respectively, and the results are comparable to the best reported values[21,27,29]. We have investigated the effects of Ta and film thickness on the temperature dependent critical current (Ic) by using Ginzburg–Landau (GL) theory[32] and we have found that the Ic and the PSLs vary in a similar fashion with Ta and the film thickness

Methods

Results

Conclusion