Low Temperature Fabrication of Diamond Films by CVD Method with Laser Induced Surface Reaction

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The novel apparatus was designed and manufactured for thermal desorption and laser induced desorption. This apparatus has 4 kinds of inlet window through which laser beam can irradiate onto the sample (incident angle : 0-60o), XYZθ sample stage (detection angle : 0-80o), time-of-flight and/or quadrupole mass spectrometer, and sample heating system up to 1400oC. The dosing system, by which the sample surface can be modified, is the thermal cracking system through hot W tube which was replaced as a part of gas introduction tube, since the gas molecule can be dissociated on the inner wall of hot W tube. Therefore, we can choose either method to control the sample surface termination, using the thermal dissociation of molecules on hot sample surface or atomic flux generated in thermal cracking system.Using this apparatus both for thermal desorption and for laser induced desorption, the dangling bonds on the sample surface was terminated by the thermal dissociation of deuterium on 1300K sam … More ple. Then, the thermal desorption spectrum of deuterium molecules was detected from the D-terminated surface. The termination structure of sample surface after dosing was confirmed by the result of thermal desorption spectra.On basis of the results and speculation of thermal desorption measurement, laser induced desorption spectrum was detected using Nd : YAG pulse laser (fundamental - 4th harmonic wave). H2 desorption of H-terminated, CO and CO2 from O-terminated diamond crystal tried to be measured. After the sample was heated up to 200℃ to desorb physiabsorbed H2O and/or CO, a variety of lased wavelength and energy density of laser pulses were irradiated onto the sample. In case of the fundamental, 2nd, and 3rd harmonic wave, we could not detect any desorption spectra. Although we could detect desorption spectra in case of the 4th harmonic wave, it was not due to the desorption by the laser induced reaction at the surface bond, but due to the thermal desorption by the sample heating as a result of the absorption of laser pulse at the defects in diamond crystals. Less