Tungsten-Silicon Thin Films Prepared by Magnetron Co-Sputtering

Superconducting nanowire single photon detector (SNSPD) is a kind of highly sensitive photodetector which uses the nonequilibrium Thermo-electronic effect in superconducting nanowire to detect single photon signal. It has the characteristics of low dark count, fast detection speed, wide response spectrum and high efficiency. It is a research hotspot in the field of single photon detection technology.

At present, there are mainly methods for preparing a tungsten-silicon thin films: a chemical vapor deposition method, an electron beam evaporation method, a sputtering method, and the like. Among them, the effect prepared by the magnetron co-sputtering method is better, and this process requires the use of a tungsten target. The preparation process is as follows:

(1) Target selection

Block W and Si with a purity of 99.999% were selected as targets for magnetron co-sputtering, and the target was placed in a magnetron co-sputtering chamber;

(2) Substrate processing

Si was selected as the substrate, and the substrate was sequentially soaked in acetone, alcohol and deionized water, and washed with power of 100 W for 10 minutes. After being blown dry, it was sent to the ion milling chamber of the magnetron co-sputtering apparatus, and argon ions were used. The surface was further cleaned and argon gas was introduced. The ion source acceleration voltage was 500 V, the ion beam current was 20 mA, and the cleaning time was 3 minutes. After the ion milling is finished, it is sent to the magnetron sputtering chamber;

(3) Preparation of WSi film

The WSi film was prepared by co-sputtering, using the conditions shown in Table 1, the sputtering time was 15 min, and the thickness of the WSi film was 73 nm.

The magnetron co-sputtering method can flexibly adjust the composition of W and Si in the WSi film to control the superconducting properties of the prepared film. Starting the high-speed motor on the sample stage, adjusting the speed of the sample stage and the distance between it and the target also ensure the uniformity of the film and good superconducting performance, which lays a foundation for the preparation of highly sensitive SSNPD devices, and hopes to be longer. Wavelengths achieve high detection efficiency, and WSi films can also be used to prepare a variety of highly sensitive detectors such as superconducting microwave dynamic inductance detectors (MKID).

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