Carbon ion irradiation effect on the chemical and electrical properties of pentacene organic film on Si substrate is investigated by means of furrier transformation infrared spectrometry (FTIR) and Van der Pauw method. In this study, pentacene film is grown by vacuum evaporation method at a substrate temperature of 80 ^oC with a deposition rate of 0.05 nm/s. The thickness of film is 200 nm. X-ray diffraction reveals that thin films phase is dominant in the as-grown film. The grown pentacene films are irradiated by carbon ions with the energy of 1.0 MeV at the dose range from 1 x 10¹² to 1 x 10¹⁵ /cm² at room temperature. During carbon ion irradiation, the ion current is settled at 1.8 μA for the area of 26 cm² to fix the dose rate for each carbon ion dose and to avoid the elevation of temperature of sample. The influence of carbon ion irradiation on chemical properties is monitored with signals of aromatic ring related vibrations of out-of-plane C-H bending at 732 and 907 cm^-1 observed in FTIR spectrum. The signals of aromatic ring related vibrations of out-of-plane C-H bending is obviously observed up to the carbon dose of 1 x 10¹³ /cm² with the small decrease in intensity. The samples irradiated at dose larger than 1 x 10¹⁴ /cm², no signals at 732 and 907 cm^-1 are observed. The sample irradiated at a dose of 1 x 10¹⁴ /cm², however, is still high sheet resistance above 1 GΩ/sq. even though the chemical property of pentacene film is mostly destroyed by carbon ion irradiation. The pentacene film irradiated at a dose of 1 x 10¹⁵ /cm² shows the change in color from purple to gray due to the irradiation defects and sheet resistance as low as 100Ω/sq. It is concluded that the chemical property of pentacene is much sensitive than electrical property for ion irradiations.

Tomohisa Yabe*, , 
Yuki Sakamoto, , 
Tomoaki Nishimura, , 
Masataka Satoh, Hosei University, Japan

*presenting author