MEASUREMENT OF ELECTRON-TRANSPORT COEFFICIENTS IN TETRAETHOXYSILANE BY A DOUBLE-SHUTTER DRIFT-TUBE METHOD

The ratio of the Townsend first ionization coefficient to the gas dens ity alpha(T)/N, the mean-arrival-time drift velocity W-m and the produ ct of the longitudinal electron diffusion coefficient and the gas dens ity NDL in tetraethoxysilane (TEOS) vapour have been experimentally de termined over a wide range of E/N from 14 to 6000 Td (1 Td = 10(-21) V m(2)) by a double-shutter drift tube technique using an arrival-time spectra (ATS) analysis. The result shows that the present values of al pha(T)/N are in excellent agreement with those previously measured by the steady-state Townsend method in an E/N range of 450-2000 Td. Value s of W-m and NDL in the TEOS vapour are reported for the first time in the present paper. It is revealed that W-m takes an almost constant v alue at 140 Td < E/N < 300 Td but monotonically increases in the other E/N ranges in the present measurement. The ratio of the longitudinal diffusion coefficient to the electron mobility D-L/mu is also deduced. The result shows that the mean electron energy in the TEOS vapour is very low, which suggests that inelastic collisions between electrons a nd the TEOS molecule occur more frequently even in a low-electron-ener gy region.