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Deposition of high-quality ultra-thin NbN films at ambient temperatures

Sascha Krause (Institutionen för rymd- och geovetenskap, Avancerad mottagarutveckling) ; Vincent Desmaris (Institutionen för rymd- och geovetenskap, Avancerad mottagarutveckling) ; Denis Meledin (Institutionen för rymd- och geovetenskap, Avancerad mottagarutveckling) ; Victor Belitsky (Institutionen för rymd- och geovetenskap, Avancerad mottagarutveckling) ; Mariusz Rudzinski ; Eckhard Pippel
25th International Sympsoium on Space Terahertz Technology, ISSTT 2014; Moscow; Russian Federation; 27 April 2014 through 30 April 2014 p. 139-140. (2014)
[Konferensbidrag, refereegranskat]

This paper discusses the possibility of growing NbN ultra-thin films on Si-substrates and AlxGa1-xN buffer-layers by means of DC magnetron sputtering without intentional substrate heating. Resistance-temperature measurements were carried out and the superconducting properties such as Tc, ΔTc and R□ were deduced while HRTEM gave insight into the crystal structure and film thickness. The adjustment of the partial pressure of argon and nitrogen was found to be critical in establishing a reliable deposition process. The quality of the interface between the NbN film and the substrate was improved by optimizing the total pressure while sputtering, and is therefore particularly valuable for phonon-cooled HEB heterodyne receivers. NbN films of 5 nm thickness were obtained and exhibited a Tc from 8K on Si-substrates, and up to 10.5 K on the GaN buffer-layers. This result is significant since the absence of a high-temperature environment permits the establishment of more complex fabrication processes for intricate thin-film structures without compromising the overall integrity of e.g. dielectric layers, or hybrid circuitries with e.g. SIS junctions.

Nyckelord: epitaxial ultra-thin NbN, buffer-layer GaN



Denna post skapades 2015-01-12. Senast ändrad 2015-11-11.
CPL Pubid: 210508