Thin films refractory materials which has a crystal structure can be prepared by a sputtering method.
The purpose of the present research is to design and construct a sputtering system for the deposition of ZnO piezoeletric thin film by a reactive sputtering in a gas mixture of Ar and $O_2$. In the design of a sputtering system, various sputtering conditions are considered. The maximum output power and voltage of a constructed system is 1 KW and 2 kV, respectively. A gas flowmeter whose maximum flow rate is 100cc/min is used to sustain a pressure in a sputtering chamber, and a gas buffer chamber is used in fixing a gas composition ratio to a constant value.
In this experiment, the composition ratio of $O_2$ is changed from 10% to 50% by a step of 10% and the substrate temperature is varied between 100℃ and 400℃ by a step of 100℃ and a sputtering time is increased from 2 hours to 12 hours by a step of 2 hours. The sputtering deposition rate is maintained at 1650 Å/hr.
The transmittance of deposited film is measured by using a spectrophotometer (Cary 17). It has fairly high transmittance in the range of 4400Å-8000Å but falls steeply near zero at about 3850Å. An attempt is made to deposite of ZnO film by thermal evaporation technique using electron beam. But the film obtained gave metalic reflection indicating decomposition of ZnO to Zn and oxygen gas.
By X-ray diffraction method, a deposited film is found to have a mixed crystal structure of (100), (002) and (101) orientations in both cases of the gas composition of 80% : 20% and 60% : 40% (Ar : $O_2$).
