Sputtering, Superconducting Films

The best superconducting films are obtained on substrates such as SrTiOs, MgO or ZrOz. Some authors have succeeded in the preparation of films on Si, but using a MgO buffer that was first sputtered onto the substrate (38). 

Ceramic superconducting films are divided into three classes, Bl-type compounds, ternary compounds, and high-temperature oxide superconductors. The Bl-type (NaCl-type structure) compound superconductors consist of nitrides and carbides with 5A, 6A, and 7A transition metals, such as TiN, ZrN, HfN, VN, NbN TaN, MoN, WN, TiC, ZrC, HfC, VC, NbC, TaC, MoC, WC, NbNi tC t, hex-MoN, and hex-MoC. Regarding the thin-film material, it is notable that NbN and NbN] (C ( (x = 0.08 and 0.15) have superconducting critical temperature, T, values of 17.3 and 17.8 K, respectively. The deposition method used is almost always sputtering or CVD. The properties of films deposited by the former method are superior. A highly reliable Josephson device was realized with an NbN film. 

R. Frerichs, Superconductive films by protected sputtering of tantalum or niobium,... 

Gilbert, L.R., Messier, R. and Roy, R., Superconducting BaPbj xBixOs Ceramic Films Prepared by R.F. Sputtering. Thin Solid Films 54 129 (1978). 

Suzuki, M., Murakami, T. and Inamura, T., Preparation of Superconducting BaPbj xBixOs Thin Films by RF Sputtering. Jpn. J. Appl. Phys. 19(5) L231 (1980). 

Oveidoped superconducting Nd2.xCexCu04,s (NCCO) (x = 0.17) thin films have been fabricated by using a planar dc sputtering technique. Current-voltage (I-V) characteristics and critical current densities Jc have been measured as function of the perpendicular magnetic field at different temperatures. Films with critical temperatures around 10 K and critical current densities above 10 A/m at T = 2.1 K have been obtained. 

Radiation damage Superconductivity of bombarded metals Variations of thin film properties Simulation of radiation damage e.g. in nuclear power plants Radiation Chemistry Ion sputtering Ion reflection Radiation decomposition of gases... 

Ghosh and Douglass (1977) have prepared by rf sputtering R,tGei, t (0.2 films deposited onto hot substrates (1020 K). With R = Y and x = 0.32 (i.e. YGe2) they have observed by resistance measurements a superconducting transition temperature of 3.8 K. With R= La and an alloy of the LaGe2 composition this temperature is 2.6 K. 

Christner et al. (1979) have prepared their samples by dc sputtering and described their experimental procedure in detail. They have minimized the contamination by oxygen which can influence the physical properties. The X-ray diffraction patterns show the formation of the ErRli4B4 compound and a small amount of RhB. The composition has been also studied by AES. The superconducting transition temperature varies from 6.0 to 7.8 K, which is somewhat different from the bulk (8.7 K). One film exhibits such a temperature and returned to the normal state at about 1.0 K (in the bulk state the change to the magnetic state is 0.9 K). Another sample, exhibiting the presence of RhB, has a transition temperature of 4.5 K. 

By cosputtering Cr and BN by magnetron radiofrequency sputtering, amorphous Cr/BN films are obtained which have superconducting transition temperatures up to 1.14 K and an orbital contribution (i.e., (dHc2 /dT)jc) as large as 49 kOe/K. In order to be amorphous, the boron nitride content in the film must be >15%. The same behavior is observed with Mo/BN films [53]. 

NbN/BN granular films are sensitive, high-speed detectors for pulsed far infrared radiation. These films are deposited on sapphire or quartz substrates by reactive radiofrequency sputtering of a split Nb/BN target in an Ar/N2 atmosphere. These devices can also be operated in the superconducting or resistive region critical temperatures range between 1.6 to 15 K,... 

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