Toshio Takabayashi

X-ray imaging camera tube using sputter-deposited CdTe/CdS heterojunction

CdTe heterojunction devices have been fabricated for the first time by an RF sputter deposition method for application to X-ray imaging sensors. The electrical resistivities of sputter-deposited polycrystalline CdS and CdTe films are greater than 10/sup 6/ Omega -cm and 10/sup 9/ Omega -cm, respectively. The fabricated CdS/CdTe heterojunction sensor shows a good diode characteristic and a high sensitivity to X-ray radiation. An X-ray imaging camera tube consisting of CdS/CdTe heterojunction photoconductive target shows three times larger responsivity to X-rays than the conventional PbO X-ray tube. The dark current density of the device is observed to be lower than 10 nA/cm/sup 2/ at 20 V target voltage at room temperature. >

Vidicon Type X-ray Imaging Sensor Using a Highly Sensitive Cadmium Telluride Photoconductive Film.

A one-inch X-ray vidicon (imaging camera tube) with a polycrystalline cadmium telluride (CdTe) photoconductive target has been developed. This vidicon has a 10.5μm thick CdTe layer deposited by RF sputtering and can attain an X-ray signal current of about 200 nA/cm2 for 2.58 mC/kg/min (10R/ min). This value is higher than the 45 nA/cm2 of conventional PbO X-ray vidicons. The dark current is about 5 nA/cm2 at a target voltage of 35 V at room temperature. The resolution of the device exceeds 251p/mm (20μm). In addition, by using a sputtering technique which can obtain large and uniform film, simultaneous deposition of many conventional and large vidion targets can easily be performed.