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Nanostructural “cauliflower-like” diamond deposited in HFCVD closed system
|Tetyana V. Semikina|
Institute of Semiconductor Physics, NAS of Ukraine, Kiev, Ukraine (ISP), 45 pr. Nauki, Kyiv 03028, Ukraine
Nanostructural “cauliflower-like” diamond particles were obtained by hot filament chemical vapour deposition (HFCVD) methods from vapour of liquid carbon sources (acetone, butyl alcohol and ethanol) and hydrogen-rich atmosphere in closed system. The pressure of vapour of carbon liquid sources was changed from 3 to 10 Torr but the hydrogen pressure varied in wide range 294 – 600 Torr to investigate the influence of hydrogen and total pressure on running process. The process was carried out on two types of substrate: silicon and Al2O3 ceramics to determine the role of substrate on process of nanodiamond formation. Time of deposition included 5, 7, 10, 30 min.
Thus the novelty of our experiment based on the fact that nanostructural diamond was deposited in closed HFCVD system from vapour of liquid carbon sources in hydrogen atmosphere without argon on Si and Al2O3 ceramics substrates.
Cauliflower like diamond particles were obtained from all types of carbon liquid sources on Si substrate and from vapour of acetone on Al2O3 ceramics substrate. The diamond particles were characterized using field-emission scanning electron microscopy (SEM) and micro-Raman spectroscopy. Raman spectrum exhibits a first-order diamond peak centred at 1330-1332 cm-1. For all samples it was observed the wide signals in the range at 1400-1600 cm-1 that testify graphite presence during the deposition process. For example SEM image of obtained diamond particles deposited on Al2O3 substrates for 30 min demonstrates that size of second diamond particles forming cauliflower particles varies from 70 nm to 1.4 mm. In experiment under deposition time 10 min for this type of substrate the size of second diamond particles was lesser (50-70 nm). For deposition on Si substrate the clear dependence between process time and size of second diamond particles was not observed.
Because the total pressure was varied in wide range and we deposited the nanostructural diamond for all total pressure variation we assume that ability to get the nanodiamond is not very sensible to total pressure. The dependence between size of nanodiamond and total pressure should exist. We observed that decreasing of total pressure leads to reduction of cauliflower-like diamond size and consequently secondary diamond particles formed it. The detailed analysis of hydrogen and hydrogen pressure influence will be presented.
We consider that one from the main technological parameters leading to nanodiamond formation is temperature of space near substrate and on the substrate surface. The substrate in our experiment was heated gradually and the substrate temperature controlled from backside by thermocouple rose from 30 to 700 -780 0C rather fast. But the processing temperature near the surface substrate probably reached the value 1200 0C that is the temperature for second diamond particles formation. The process temperature was observed with two-coloured pyrometer (CHINO, IR-AQ and IR-GAG) and consequently we could not determine accurately the temperature close to the substrate surface.
Thus it was found technological conditions allowed to deposit nanostructural diamond from liquid carbon sources of different types on Si and Al2O3 substrates that is new result approaching us to nanodiamond deposition industrial application.
Keywords: Nanostructural Diamond, Liquid Carbon Source, Hot Filament CVD
Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Tetyana V. Semikina
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth
Submitted: 2007-01-09 15:34 Revised: 2009-06-07 00:44