Kotaku Hayashi

Carrier Mobilities in Insulating Polymers Measured by Time of Flight Method

Carrier mobilities of several insulating polymers such as PET, PS were studied by the time of flight method using pulsed electron beam bombardment. For example, the mobilities obtained in an electric field of 1~2 MV/cm were 2×10-5 cm2/Vsec for the electron and 1×10-4 cm2/Vsec for the hole at 27 °C in PET with the activation energy around 0.3 eV. At low field mainly the slow carrier component due to detrapping was observed, which apparently gave a much lower mobility. The carrier lifetime was also estimated from the Hecht curve. It was found that the quantum yield (number of induced carriers per impinging electron) was influenced seriously by the molecular structure.

Carrier mobility in vinylidenefluoride-trifluoroethylene copolymer

The carrier mobility of a ferroelectric Vinylidenefluoride-Trifluoroethylene copolymer (VDF: 54 mol%) was measured by the time-of-flight method after irradiation by a KrF excimer laser. The hole and electron mobilities were estimated to be 3×10-6 cm2/Vs and 7×10-6 cm2/Vs, respectively.

Mobility Measurements in Polymers by Pulsed Electron Beams

Carrier mobilities of several polymers were studied by the time of flight method using a pulsed electron beam. The obtained mobilities at the field of 1 MV/cm were 2.7 × 10−5 cm2/Vsec for electron and 1.2 × 10−4 cm2/Vsec for hole in PET, 1.4 × 10−4 cm2/v sec for electron and 7 × 10−5 cm2/Vsec for hole in PS, and 1.6 × 10−4 cm2/Vsec for electron and 6.3 × 10−5 cm2/Vsec for hole in PEN at room temperature respectively. Schubweg and quantum yield of the carrier were also studied. It was found that the quantum yield (number of induced carriers per impinging electron) was influenced seriously by the molecular structure.

Mobility measurernents in polymers using pulsed electron beams

Although the mobility in polymers using various methods has been reported by several authors, the values of mobility are not consistent among each other.1,2