Growth of Polycrystalline n- CrSe2 Nanosheets Onto p –Si Substrates and their Applications as Rectifiers and Gigahertz Band Filters

Abstract

In the current study polycrystalline nanosheets of CrSe2 of thicknesses of 100 nm are deposited onto p− type silicon substrate by a vacuum evaporation technique under a vacuum pressure of 10–5 mbar. Experimental and theoretical structural investigations have shown the preferred growth of trigonal CrSe2. The unit cell parameters being a=b=3.520 Å,c=5.889 Å and P3m1(164) fts well with the standards of trigonal CrSe2 structure. Nanosheets of chromium selenide displayed low defect density of the order of 1010 lines/cm2 along the a− and b axes. Surface morphology studies have shown that CrSe2 nanosheets is composed of spherical grains of average sizes of 200 nm. Optically the interfacing of the n– type CrSe2 nanosheets with p− type Si results in formation of a conduction and valence band ofsets of 0.95 eV and 0.47 eV, respectively. These band ofsets were found sufcient to allow running the Si/CrSe2 interfaces as pn junction devices. The devices displayed a biasing dependent rectifcation ratios (asymmetry). The ratios which reached value of 70 can be varied with the applied voltage. Deep analyses of the current transport mechanism of these rectifers have shown the domination by thermionic and tunneling mechanisms under forward and reverse biasing conditions, respectively. Moreover the pn junction device showed features of band flters with cutof frequency values suiting gigahertz technology making the device attractive for multifunction operations