Stoichiometric thin films of In2S3 were prepared by the thermal evapor
ation technique; the as-deposited films were non-crystalline and the c
rystallinity was built in on annealing at 423 K. The crystal structure
as determined by both x-ray and electron diffraction showed that tetr
agonal films of beta-In2S3 phase were obtained. Both dark electrical r
esistivity rho and thermoelectric power (Seebeck coefficient S) were m
easured for films before and after annealing. The In2S3 films showed n
-type conduction; the existence of two distinct activation energies De
lta E-1 and Delta E-2 belongs to two types of level: a shallow level o
f Delta E-1 = 0.319 eV before annealing and Delta E-1 = 0.166 eV after
annealing and deep levels of Delta E-2 = 0.61 eV for as deposited fil
ms and Delta E-1 = 0.515 eV for annealed film. The deep level was also
detected by the space charge limited current technique and the trap d
ensity N-t is found to be 3.92 x 10(22) m(-3). The obtained results ar
e explained on the basis of an energy diagram of beta-In2S3 proposed b
y Garlick.