Optoelectronic properties of thin film CdS formed by ultraviolet and infrared pulsed-laser deposition

Abstract

Thin CdS films on glass are formed by ultraviolet (UV) and infrared (IR) pulsed-laser deposition (PLD) at 355 and 1064 nm with a repetition rate of 10 Hz and a pulse width of 10 ns and 150–180 μs, respectively. The applied laser fluence is kept in the range of 2–4 J cm−2. By UV-PLD, the orientation of the c-axis with respect to the glass surface is adjustable via laser fluence, resulting in perpendicular and parallel oriented films at 2 and 4 J cm−2, respectively. The orientation of IR-PLD samples is maintained perpendicularly, independent of the fluence. The optoelectronic properties of the films are studied by photocurrent (PC) and photoluminescence (PL) spectroscopy at 300 K. The PC of the UV-PLD samples reflects the turn of the c-axis, i.e. the absorption anisotropy, of CdS. The IR-PLD films, however, do not show PC because of high dark conductivity. The UV-PLD samples show PL in the range (2.27–2.45 eV). The emission below 2.45 eV is caused by formation of recombination centers. Notably, the film formed at 3 J cm−2 emits the spectral sum of the films formed at 2 and 4 J cm−2. The IR-PLD samples show green emission (2.493 eV) clearly above the CdS bandgap due to band filling. The results pave the way for the creation of smart photonic gratings, which exhibit locally tunable optoelectronic properties.