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Abstract: A diamond heat spreader made of nanoscale diamond tips on a diamond/Si substrate has been fabricated by planar microwave plasma enhanced chemical vapor deposition. The nanoscale diamond tips are in a conelike shape, which are ~1 µm in height and their average diameter at the bottom is ~200 nm. The nanoscale diamond tips act as a nanoscale “fin structure”, which provide extended surface area to dissipate heat away. A concept of “quasi thermal resistance” is developed to characterize the thermal spreading properties of the nanoscale diamond tips/diamond/Si structures at various air flow rates in a wind tunnel. Experimental results indicate that nanoscale diamond tips help to improve the thermal spreading properties, especially at zero air flow rate. The improvement is attributed to the large surface area of nanoscale diamond tips. At an air flow rate higher than zero, the improvement of thermal spreading properties diminishes. [Copyright &y& Elsevier]

Abstract: Vertically oriented nano-scale diamond tips were synthesized on the micro-size diamond particles in a planar microwave plasma enhanced chemical vapor deposition chamber by varying synthesis time, bias voltage, and gas ratio. Diamond particles were embedded in the thin layer of Ni on an Al plate and then followed by the synthesis of nano-scale diamond tips. Vertically oriented nano-scale diamond tips were selectively synthesized on diamond particles, which were justified by the C KLL Auger spectra taken by an Auger nanoscope. On top of the Ni surface surrounding diamond particles, carbon was deposited in the form of amorphous carbon, rather than diamond, which was confirmed by the corresponding C KLL Auger spectra. The qualities of nano-scale diamond tips were characterized by the diamond characteristic peak at 1332 cm−1 in the Raman spectra. The morphologies of nano-scale diamond tips strongly depend on the bias voltage. The optimum bias voltage to achieve nano-scale diamond tips of bottle-like shape is about −250 V. The density of nano-scale diamond tips can be tuned primarily by varying the gas ratio of Ar/CH4/H2. [Copyright &y& Elsevier]