VACUUM-DEPOSITED CADMIUM SULFIDE THIN FILMS,

Cadmium sulfides was vacuum-deposited onto glass substrates at approximately 0.00002 torr using electron beam heating. Initial resistivities were in the range 0.1 to 1 ohm-cm. After heating in vacuum at 360 to 370C for 12 hr, the resistivities increased to the range 0.3 to 300,000 ohm-cm. To correlate resistivity with crystal structure, the cadmium sulfide films were studied by means of X-ray and electron diffraction, and spectrophotometry. It was found that these cadmium sulfide films were hexagonal and highly oriented with the c-axis perpendicular to the plane of the substrate. Grain size perpendicular to the c-axis was much less than 100 A after deposition onto room-temperature substrates, and increased to 100 to 200 A in diameter after heat treatment. To determine the type of contact the commonly deposited metals make to cadmium sulfide, a mask changer was employed to allow the deposition of layerized arrays of metal-cadmium sulfide-metal in a single pumpdown. Aluminum, indium, silver, and gold were thereby deposited in several different electrode combinations. Combinations having aluminum as one or both of the electrodes exhibited rectifying characteristics all other combinations exhibited ohmic characteristics. Author