Normal-Metal–Insulator–Superconductor Tunnel Junction With Atomic-Layer-Deposited Titanium Nitride as Superconductor

Author

Torgovkin, Andrii ; Chaudhuri, Saumyadip ; Malm, Jari ; Sajavaara, Timo ; Maasilta, Ilari J.

Author_Institution

Dept. of Phys., Univ. of Jyvaskyla, Jyvaskyla, Finland

Volume

25

Issue

3

fYear

2015

fDate

42156

Firstpage

1

Lastpage

4

Abstract

We report the fabrication of 70–350-nm-thick superconducting titanium nitride (TiN_x) films using the atomic layer deposition (ALD) technique and the subsequent fabrication of normal metal–insulator–superconductor (NIS) tunnel junction devices from the ALD films. The films were deposited on a variety of substrates: silicon, silicon nitride, sapphire, and magnesium oxide. Superconductivity, with transition temperatures $(T_{C} )$ ranging from 1.35 to 1.89 K, was observed in all films. $T_{C}$ was found to depend on both the substrate type as well as film thickness. Cu-TiO_x-TiN_x NIS tunnel junction devices were fabricated from the TiN film deposited on silicon, using electron beam lithography and shadow angle evaporation techniques. These devices exhibit temperature-dependent current–voltage characteristics and good thermometric response from 0.1 K to slightly above $T_{C}$ . Nonlinearity in the current–voltage characteristics was observed even at temperatures as high as 5 $T_{C}$ , indicating the presence of a pseudogap in these TiN_x films.

Keywords

atomic layer deposition; copper; electrical conductivity; electron beam lithography; superconducting junction devices; superconducting materials; superconducting thin films; superconducting transition temperature; superconductive tunnelling; thin film devices; titanium compounds; vacuum deposition; ALD films; Al₂O₃; Cu-TiO_x-TiN_x; MgO; Si; SiN; atomic-layer-deposited titanium nitride; electron beam lithography; film thickness; magnesium oxide substrates; normal-metal-insulator-superconductor tunnel junction devices; pseudogap; sapphire substrates; shadow angle evaporation techniques; silicon nitride substrates; silicon substrates; size 70 nm to 350 nm; superconducting titanium nitride films; superconducting transition temperature; temperature-dependent current-voltage characteristics; thermometric response; Films; Junctions; Substrates; Superconducting films; Superconducting transition temperature; Temperature; Temperature measurement; Atomic layer deposition; pseudogap; superconductivity; thermometry; thin film; tunnel junctions;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/TASC.2014.2383914

Filename

6991555