Both CdS and ZnS crystals are Ⅱ-Ⅵ semiconductors and photonic materials having the direct band gaps.Since the wavelength corresponding to the band-gap of CdS is green 500 nm that is very sensitive for human eyes

the CdS thin film is useful for the sensor and the light source.For the CdS thin film produced by pulsed laser deposition (PLD)

we first demonstrated the laser oscillation at room temperature excited with He-Cd laser.On the other hand

ZnS has been used for the fluorescence materials with the various doped elements.The band-gap of ZnS is so large (3.6 eV) that has been applied for the quantum well

the blue LED and the optical waveguide.Zn

1-x

Cd

x

S alloy thin films were prepared on quartz substrate by low-pressure metalorganic chemical vapor deposition (MOCVD).The x values of Zn

1-x

Cd

x

S are 0

0.02

0.44

0.59

0.83

0.91 and 1.X-ray diffraction (XRD) spectra indicate that all the as-grown alloys with hexagonal wurzite structure was obtained.As the Cd content increases

the luminescence peaks of the samples redshift from 3.66 eV to 2.43 eV in the photoluminescence (PL) spectra.Based on the PL peak position of the alloy with different Cd composition

the relation of Zn

1-x

Cd

x

S emission peak with x was obtained as E

g

(Zn

1-x

Cd

x

S)=3.61-1.56x+0.38x

2

.The dependence of the PL peak position and the full width at half maximum(FWHM) of the diffraction peak and PL peak on Cd composition were also discussed.It is found that when x increases from 0 to 1

the PL peak position changes from 3.66 eV to 2.43 eV;but the FWHM increases and reaches a maximum when x=0.83

then it decreases sharply.