Chemical deposition of bismuth selenide thin films usingN,N-dimethylselenourea

Abstract

Good quality thin films of bismuth selenide of thickness up to 0.28 µm were deposited from solutions containing bismuth nitrate, triethanolamine and N ,N -dimethylselenourea maintained at temperatures ranging from room temperature to 40 • C. X-ray diffraction patterns of the samples annealed at 200 • C in air match the standard pattern of hexagonal Bi 2 Se 3 (paraguanajuatite, JCPDS 33-0214). The films exhibit strong optical absorption corresponding to a bandgap of about 1.7-1.41 eV in the as-prepared films. These values decrease to about 1.57-1.06 eV upon annealing the films at 200 • C for 1 h in nitrogen. As-deposited, the films show high sheet resistance (∼10 12 −1 ) in the dark. Annealing the films in air or in nitrogen enhances the dark current by about seven orders of magnitude; the resulting dark conductivity is about 10 −1 cm −1 . This enhancement in conductivity results from improved crystallinity as well as from partial loss of selenium.

Chemical Synthesis and Properties of Novel Bi2Se3 Nanostructures and Microplatelets

“…The observed values of E g are shown as an inset in Figure 5 and the range is consistent with those reported earlier through other deposition methods 2.25 eV [1], 1.5 eV [3], 2.35 eV [14], and 1.7-1.41 eV [21]. There was a red shift towards lower energies with increasing substrate temperature for the samples.…”

Thin‐Film Semiconductors Deposited in Nanometric Scales by Electrochemical and Wet Chemical Methods for Photovoltaic Solar Cell Applications

“…The fabrication of Bi 2 Se 3 thin fi lms using the CBD method was also carried out [280] for a deposition electrolyte consisting of 7 ml of 0.5 M Bi(NO 3 ) 3 solution, 7 ml of 50% TEA, and 20 ml of 0.07 M N , N -dimethylselenourea solution prepared freshly in 0.01 M Na 2 SO 3 , with the balance made up of water. Films of 0.2 µ m may be deposited in about 9 hours at 40 ° C.…”

98/03942 Semiconductor thin films by chemical bath deposition for solar energy related applications

“…Bi Se thin films [41]: 7 ml of 0.5 M Bi(NO ) solution, 7 ml of 50% triethanolamine, 20 ml of 0.07 M N,N-dimethylselenourea solution prepared freshly in 0.01 M Na SO , and the rest water. Films of 0.2 m may be deposited in about 9 h at 40°C or in about 60 h at room temperature.…”

“…2 illustrates the quality of the films: the transmittance, ¹( )%, and the specular reflectance, R( )%, add up to nearly 100 at wavelengths longer than the threshold for optical absorption across the band gap. Arrows in the figure indicate the values listed for the optical band gap 1.03 eV (1204 nm) and 1.88 eV (659.5 nm) for Bi Se and Sb S , respectively [41,43]. …”