Study of the effects of low-energy electron bombardment during the chemical vapor deposition of diamond
- PDF / 184,431 Bytes
- 3 Pages / 612 x 792 pts (letter) Page_size
- 7 Downloads / 198 Views
The effects of low-energy electron bombardment during the chemical vapor deposition of diamond were studied. The film growth was monitored in real time with in situ phase-modulated ellipsometry, in order to trigger the electron bombardment at different growth stages. Ex situ Raman spectroscopy and scanning electron microscopy were employed to evaluate the crystalline quality and the morphology of the grown films, respectively. The results indicated that triggering the electron bombardment after high-quality scattered diamond crystallites had formed results in finely grained smoother films of similar diamond yield and crystalline quality as those grown without bombardment. However, the electron bombardment deteriorates the film crystalline quality and the diamond yield when it was triggered from the start of deposition. I. INTRODUCTION
II. EXPERIMENTAL
Polycrystalline diamond is already a common material in many tribological applications. Its extreme hardness combined with chemical inertness, wide spectral transparency, and high electron and hole mobilities also make diamond an excellent candidate for various electronic and optical applications.1 However, polycrystalline diamond films typically show rough surface morphologies that make it difficult to deposit metallic structures on them. Therefore, besides the well-known current problem of finding a suitable n-type dopant for diamond, the surface roughness of currently available films can be a limitation for its electronic applications when it comes to making devices on these surfaces.2 While devoting efforts toward the n-type doping of diamond,3 we are also trying to find ways to overcome the roughness issue.2 Electron-assisted chemical vapor deposition (CVD) of diamond was previously shown to enhance the formation of nucleation centers and to increase the growth rate.4 In this article, we present results on the effects of lowenergy electron bombardment during diamond growth over the film crystalline quality and morphology. The film growth was monitored with in situ phase-modulated ellipsometry5,6 through the effective extinction coefficient (k) at 1.96 eV photon energy, in such a way that we could determine the developmental stage the film is at in real time. Taking advantage of this in situ monitoring, we triggered the electron bombardment over the growing surface at different growth stages in order to study the changes induced in film morphology and crystalline quality.
The diamond films employed in this study were prepared in a hot-filament chemical-vapor-deposition (HFCVD) system, which is described in more detail elsewhere.7 The films grew on Si(100) substrates kept at a temperature of 600 °C. We used a mixture of 0.3% CH4 in H2 kept at 20 torr and flowing at 200 sccm, that has been found to produce the best crystalline quality and diamond yield in our reactor. The substrates were Si disks 2.5 cm in diameter pretreated with 3-m diamond paste and washed thoroughly with methanol. The substrates were then annealed at 700 °C in vacuum (10−7 torr) to heal the d
Data Loading...
