Cd

2

SnO

4

thin films are a n-type wide-bandgap semiconductor. Thin films of the teinary oxide Cd

2

SnO

4

show the remarkable properties such as low

metal-like electrical resistivity

good transmissivity in the visible range of the light spectrum and high reflectivity in the near IR

[1-6]

. These films can be used transparent electrodes

heat mirrors and antistatic layers in optoelectronics and solar enrgy conversion technology.In this paper we report the photoluminescence properties of Cd

2

SnO

4

thin films prepared by r.f. reactive sputtering from a Cd-Sn alloy target in an Ar-O

2

reactive gas mixture. Experimental results show that the photoluminescence spectrum of Cd

2

SnO

4

thin films is very sensitive to the deposition conditions. The photoluminescence peaks exhibit a‘red shift’when oxygen concentration is increased. The variation of emission peaks of Cd

2

SnO

4

thin films may be attributed to the change of oxygen vacancy in Cd

2

SnO

4

thin films. Cd

2

SnO

4

thin films are a n-type defect semiconductor in which oxygen vacancies are believed to provide the donor state

[9

10]

. The oxygen vacancy concentration can be varied over a wide range with the change of oxygen concentration during deposition. The free carrier concentration of conduction band changes with changing oxygen vacancies. The change of the carrier concentration causes the shift of band gap according to the Burstein-Moss (BM) effect

[12

13]

and the effect of electron-electron and electron-impurity scattering

[14]

. Then

the photoluminescence peaks are shifted with the change of band gap.