Total photoyield experiments are applied to characterize p-, intrinsic, and n-type diamond with hydrogen-terminated surfaces. On all hydrogen-terminated samples a photoelectron threshold energy of 4.4 eV is detected which is discussed in detail in this letter. We attribute this threshold to the energy gap between the valence-band maximum and the vacuum level, which is 1.1 eV below the conduction-band minimum, and generally referred to as ”negative electron affinity” (NEA). Hydrogen terminated p-type and intrinsic diamond show a rise of secondary photoyield in the excitation regime hν>5.47eV. However, this is not detected on n-type diamond. We ascribe this to the formation of an upward surface band bending in the vicinity of the n-type diamond surface which acts as an energy barrier for electrons.

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We have developed a technique to form Si microstructures at preassigned positions on Si substrates. The key element of this technique is resistless patterning of ultrathin SiO2 mask layers by direct electron-beam exposure. Selective-area growth of Si was accomplished by two different chemistries: flow-modulated plasma-enhanced chemical vapor deposition (CVD) at 473 K or ultra-high-vacuum CVD at 853 K. Epitaxial deposition was achieved by the latter growth method when a mask layer with minimum thickness for deposition selectivity (approximately 0.2 nm) was employed.

Ultrathin SiO2 and SiN x layers on Si are potential mask materials for nanoscale selective-area chemical vapor deposition (CVD) in reduced dimension. This study investigates the mask-material dependence of Si nucleation processes on these ultrathin layers. Thin layers of SiO2, SiN x and SiO x N y were formed by plasma oxidation and nitridation. They were subjected to CVD processing without exposure to air, which prevented the results from being affected by surface contamination. Incubation time for nucleation was checked by both in-line Auger electron spectroscopy (AES) and atomic force microscopy (AFM). In the case of ultrahigh vacuum CVD (UHV-CVD) at 853 K, the incubation time for nucleation decreased in the order of SiO2, SiO x N y and SiN x . In the case of flow-modulated plasma-enhanced CVD (FM-PECVD) at 473 K, Si growth did not depend on the kind of the mask material. Direct electron-beam patterning of this mask layer is briefly reported. Based on the results presented, a novel bilayer mask structure is proposed.

Nano-scale diamond tip arrays on single crystals (100) are fabricated by plasma etching and their field emission characteristics are studied. We fabricate three types of structures: ordered tips with a high density, ordered tips with a low density and an unordered whisker structure. In field emission measurements, the ordered tips with a low density have better field emission than the ordered tips with a high density and the unordered whisker structure. Field enhancement factors are estimated from Fowler-Nordheim plots (βFN) and tip geometry (βtip). Although the βFN is almost the same as the βtip for the ordered tips with a low density, the βFNs of the ordered tips with a high density and the unordered whisker structure are one order smaller than the βtips. This indicates that using a tip array with a low density helps in reducing the neighboring shielding effects, thereby leading to βFN similar to βtip. We found experimentally that the tip arrangement plays an important role in the field emission from diamond.