Superconducting MgB2 thin films on silicon carbide substrates by hybrid physical–chemical vapor deposition

Abstract

We have used two polytypes of silicon carbide single crystals, 4H-SiC and 6H-SiC, as the substrates for MgB 2 thin films grown by hybrid physical-chemical vapor deposition ͑HPCVD͒. The c-cut surface of both polytypes has a hexagonal lattice that matches closely with that of MgB 2. Thermodynamic calculations indicate that SiC is chemically stable under the in situ deposition conditions for MgB 2 using HPCVD. The MgB 2 films on both polytypes show high-quality epitaxy with a Rutherford backscattering channeling yield of 12%. They have T c above 40 K, low resistivities, high residual resistivity ratios, and high critical current densities. The results demonstrate that SiC is an ideal substrate for MgB 2 thin films.

Properties of MgB2 thin films with carbon doping

“…In particular, high critical current density J c near the depairing limit has been observed in MgB 2 [2], and unlike high temperature superconductors grain boundaries in MgB 2 do not behave like weak links [3]. Although clean MgB 2 shows low upper critical field H c2 [4], in high resistivity MgB 2 films H c2 is substantially higher [5]; the critical current density J c in clean MgB 2 is suppressed by a relatively low magnetic field [6], but defects and impurities have been shown to enhance pinning [7,8]. Recently, we have developed a hybrid physical-chemical vapor deposition (HPCVD) technique, which produces in situ epitaxial MgB 2 films with T c above 40 K [6,10].…”

“…Although clean MgB 2 shows low upper critical field H c2 [4], in high resistivity MgB 2 films H c2 is substantially higher [5]; the critical current density J c in clean MgB 2 is suppressed by a relatively low magnetic field [6], but defects and impurities have been shown to enhance pinning [7,8]. Recently, we have developed a hybrid physical-chemical vapor deposition (HPCVD) technique, which produces in situ epitaxial MgB 2 films with T c above 40 K [6,10]. Because of the highly reducing H 2 ambient and the high purity B 2 H 6 source used in the HPCVD process, the technique produces very clean MgB 2 thin films with a residual resistivity at T c as low as 0.28 µ .cm [10].…”

Crystal Structure and Properties of the Oxide-Containing Magnesium Diboride Films

“…Среди таких методов -совместное испарение компо-нент из резистивных испарителей [4], а также испарение одного из компонентов из резистивного испарителя, а другого с помощью электронной пушки [5], лазерное осаждение с последующим ex situ отжигом [6], молекулярно-лучевая эпитаксия [7], магнетронное распыление мишеней [8,9], осаждение путём гибридного физико-химического испарения (hybrid physical-chemical vapour deposition (HPCVD)) [10][11][12][13]. Каждый метод имеет преимущества и недостат-ки, для сравнения в табл.…”

Nanogranular MgB2thin films on SiC buffered Si substrates prepared by anin situmethod

“…Most of these substrates are monocrystals, often rather expensive (SiC, SrTiO 3 ). So far, the best results have been obtained by Zeng et al [8] where high quality MgB 2 films were prepared using a hybrid physical-chemical vapor deposition (HPCVD) technique on top of a monocrystalline 6H-SiC substrate. To the best of our knowledge, no publication reports on the deposition of MgB 2 on SiC buffered Si substrate.…”

“…This is a challenge to look for another non-superconducting type of buffer layer on top of the "technological" Si substrate. The potential buffer layer can be chosen on the base of substrates which recently were successfully used for the preparation of MgB 2 films as sapphire [2,3], MgO [4,5], SrTiO 3 [6,7], SiC [8], and SiN [9]. Most of these substrates are monocrystals, often rather expensive (SiC, SrTiO 3 ).…”