Patent Application
20110111129
1. Field of the Invention
The present invention relates to a method for fabricating a cadmium sulfide (CdS) thin film, and more particularly to a chemical bath deposition for fabricating the cadmium sulfide thin film.
2. The Prior Arts
Cadmium sulfide is a II-VI semiconductor material with wide band gap (Eg=2.26˜2.5 eV). Cadmium sulfide is mainly applied in the solar cells, the light emitting diodes, the photoconductor sensors, the photocatalysts and the other photoelectric devices. The well-known methods for fabricating a cadmium sulfide thin film are the chemical bath deposition method, the microwave-assisted chemical bath deposition method, the vacuum evaporation method, the sputtering method, the chemical vapor deposition method, and the spray pyrolysis method.
The chemical bath deposition method comprises the steps of: (1) immersing the glass substrate in a diluted solution containing cadmium ions and sulfide ions; and (2) automatically depositing a cadmium sulfide thin film on the glass substrate. The advantages of chemical bath deposition method are that the mass production is easily available at lower costs, and the process is simple to use.
According, the present invention provides a fabricating method to precisely control the cadmium sulfide thin film, by which a high quality cadmium sulfide thin film with uniform thickness can be obtained, and the obtained cadmium sulfide thin film has excellent adhesion to the glass substrate.
The objective of the present invention is to provide a method for fabricating a cadmium sulfide thin film, in which a cadmium sulfide thin film is fabricated by using a chemical bath deposition method. According to the method of the present invention, the chemical bath including the sulfur-containing compounds and the cadmium-containing compounds is adjusted to alkaline by adding aqueous ammonia, followed by adding the buffer salts while stirring and heating, and then the glass substrate is immersed in the chemical bath such that when the immersing time is increased, the thickness of cadmium sulfide thin film will be increased, and the cadmium sulfide thin film obtained does not have a dual structure, and thereby the obtained cadmium sulfide thin film can have excellent adhesion to the glass substrate, and thereby the quality of cadmium sulfide thin film is improved. The amount of the cadmium ions contained in the chemical bath is 10 to 500 times of the amount of cadmium ions contained in the cadmium sulfide thin film, and the amount of the sulfide ions contained in the chemical bath is 5 to 100 times of the amount of sulfide ions contained in the cadmium sulfide thin film. The concentration of aqueous ammonia is 20% to 30%. The preferred pH value of chemical bath is 8 to 11, the preferred heating temperature is 60 to 90° C., and the preferred immersing time is 5 to 60 minutes.
Therefore, the cadmium sulfide thin film with a thickness of 10 to 1000 nm can be obtained, and the obtained cadmium sulfide thin film has excellent adhesion to the glass substrate.
The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings, in which:
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Referring to
The water used in Steps 10 and 60 can be the deionized water. The concentration of the aqueous ammonia used in Step 20 can be 20% to 30%. In the present invention, the cadmium sulfide thin film with a thickness of 10 to 1000 nm can be obtained, and the obtained cadmium sulfide thin film has excellent adhesion to the glass substrate.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
