Recombination process of laser produced ZnO plasma in a gas atmosphere

Summary form only given, as follows. Atomic processes of laser-produced plasmas have been extensively studied in the fields of nuclear fusion and X-ray lasers. Laser ablation has been employed in the fabrication of high-quality thin films. Atomic processes of the laser-produced plasma/plume, however, have not been well understood so far, especially, the recombination process due to the gas contact cooling, which is considered to be important for the thin film deposition In this paper we study the recombination process by observing time and spatial evolution of spectral emissions from the ZnO plume in He or O/sub 2/ gas with various pressures. The third-harmonic pulses of a Nd:YAG laser (wavelength 355 nm, pulse width 5 ns, energy 0.5 J/cm/sup 2/ per pulse) was used for the ablation of a target ZnO disk Time- and spatially-resolved emission spectra were measured with a multichannel spectrometer with a gated image intensifier and a CCD camera. By use of the gas contact cooling method, the size, density and temperature of plasma can be controlled easily. It may be helpful to grow the thin film with the desired property. Electron temperatures and densities at different spatial positions were determined from line intensity ratio methods coupled with a collisional-radiative model of helium atom Boltzmann plot of highly lying levels of Zn atom was also used for estimation of electron temperature. And the velocity of plasma was estimated by a time-of-flight method. Atomic processes in the recombination plasmas will be presented in detail.