The microstructure and electrical transport properties of immiscible copper-niobium alloy thin films

Abstract

Thin film reaction of transition metals with germaniumMutually immiscible in the solid state, copper and niobium exhibit a relatively strong clustering ͑phase separating͒ tendency in the liquid state and can therefore only be alloyed in a highly metastable form: for example, by vapor quenching. We have deposited metastable Cu-Nb alloy thin films with nominal compositions ranging from 5 to 90 at. % Nb by magnetron cosputtering. The microstructure of these films depends strongly on the composition and ranges from coarse-grained solid solutions for Cu-rich and Nb-rich compositions to phase-separated amorphous mixtures when the two elements are in comparable amounts. The crystalline Cu-or Nb-rich compositions exhibit positive temperature coefficients of resistivity ͑TCR͒ with the Cu-90 at. % Nb film exhibiting a superconducting transition with ͑T C ͒ onset ϳ 4.5 K. The amorphous films show high room temperature resistivity, a negative TCR, and composition dependent superconducting transitions. We investigate the relation between the microstructure, phase stability, and the electrical transport properties.

Microstructure and mechanical properties of CuxNb1−x alloys prepared by ball milling and high pressure torsion compacting

“…The TEM image and ED pattern show the nanocrystalline character of Nb-rich alloy with an estimated grain size of 7-10 nm. Similar microstructures by TEM of Cu x Nb 1Àx alloys with 5-10 at.% of Nb have been shown by [13,21].…”

“…It is suggested that the solution of Cu in the Nb matrix shifts the Nb (1 1 0) peak to higher angles, which results in a decrease in the lattice parameter. Banerjee et al cited a lattice parameter of 0.325 nm for a Cu-90 at.% Nb [21].…”

“…Fe, Cr, Ta, W, Nb) has been used for years to increase the relatively low intrinsic strength of copper [2][3][4][5][6][7][8][9][10][11][12][13][14][15], as well as to enhance the irradiation tolerance by forming specific Cu/Nb interfaces (Kurdjumov-Sachs) [16][17][18]. While Cu x Nb 1Àx shows very good mechanical properties and high strength [10], as well as good electrical properties [14,[19][20][21], its radiation tolerant properties as nanostructured multilayers are also of interest to the nuclear materials community [22][23][24][25].…”

“…However, the formation of a supersatured Cu-Nb solid solution through non-equilibrium processing techniques, such as vapour deposition techniques or mechanical alloying, allows a solubility of up to 15 at.% Nb in Cu and up to 25 at.% of Cu in Nb. Cu x Nb 1Àx alloys prepared by ball milling have been studied exhaustively by Botcharova et al [10][11][12][13], and more recently by Mula et al [7], Lei et al [8,9] and Banerjee et al [21]. All these studies created a 3D-Cu/Nb interface alloy, which is in contrast to a 2D layered material as prepared typically by PVD processing, accumulative roll bounding, or cold drawn [27][28][29][30][31].…”

Radiation response of amorphous metal alloys: Subcascades, thermal spikes and super-quenched zones

“…This potential describes short-range interactions using the ZieglerBiersack-Littmark (ZBL) function [22] and is therefore well adapted to simulations of radiation response. Amorphous Cu-Nb has been experimentally synthesized via ion-beam mixing [23,24] and sputter deposition [20,[25][26][27] within the composition range of $35-75% copper [26]. We model a-Cu x Nb 1Àx with x = 0.25, 0.5 and 0.75.…”