In this study, we carry out high temperature glancing angle deposition (HT-GLAD) of Fe and Al on a heated substrate with trench patterns. When vapor is incident perpendicular to the trench direction, nanowhiskers grow only on the surface exposed to the vapor and not inside the trenches. When vapor is incident at a deposition angle larger than 80° on the sidewall of the trench and not on the substrate surface, nanowhiskers grow only on the sidewall because the condition of deposition at a high temperature and a large deposition angle is satisfied only for the sidewall. Thus, we succeed in the selective growth of nanowhiskers by controlling the geometrical deposition conditions. Further, we also discuss the effect of the local deposition geometry on the growth process.Geometrically selective growth by HT-GLAD is expected to be useful for growing nanowhiskers on nano-and microstructured substrates.

We have demonstrated that the vapor-liquid-solid (VLS) growth of Ge nanowhiskers is significantly enhanced by high-temperature glancing angle deposition (HT-GLAD). At the substrate temperature of 420 °C, the Ge nanowhiskers grow on the sample deposited at the deposition angle of α = 85°, whereas no long nanowhisker grows on the samples deposited at α ≤ 73°. The kinetic growth model that takes into account the directional incidence of the vapor flux agrees with the experimental results and suggests that the atoms deposited on the side surface of the nanowhiskers play an essential role in the HT-GLAD assisted VLS growth. Supplying the atoms on the side surface of the nanowhiskers is expected to accelerate the growth of the nanowhiskers in any vapor phase growth methods, such as molecular beam epitaxy and chemical vapor deposition.

We have investigated the effect of the substrate-surface morphology on the growth of Al whiskers grown by high temperature glancing angle deposition (HT-GLAD). Before the HT-GLAD of Al at 390 °C, the morphology of the substrate was systematically modified by depositing nanocolumnar SiO 2 layer of thickness between 0 and 100 nm on the flat SiO 2 layer. Aluminum whiskers with the width of ≈ 100 nm and the length ≤ 8 µ m are found on all the samples. The number of short whiskers, which can be grown from very small nuclei, depends strongly on the thickness of the SiO 2 nanocolumnar layer and shows the maximum at SiO 2 thickness of 20 nm. On the other hand, the number of long whiskers, which requires extraordinary amount of Al than that deposited on the side surface of the whiskers, is almost independent of SiO 2 thickness. These facts suggest that the surface roughness of the substrate plays an important role in the nucleation of the whiskers and that there are some transport processes of Al, which are insensitive to the surface morphology.

We demonstrate high temperature glancing deposition (HT-GLAD) of metals on the heated substrate. It has been found that Al, Ag, Au, Fe nano-whiskers grow on the substrate of Si, SiO2, and glass substrates. The robustness in the selection of materials suggests that the HT-GLAD is a universal method to grow nano-whiskers of various metals. We also demonstrate the selective growth of the nano-whiskers on the substrate with micro-trench patterns. The metal nano-whiskers are useful for the nano electromechanical devices and vacuum microelectronics.

In this experiment, we demonstrate the high-temperature glancing angle deposition (HT-GLAD) of metals. Whiskers of Cu, Ag, Au, Mn, Fe, Co, Ni, Zn, and Al, grow on substrates of SiO2. Deposition at the glancing angle and at temperatures higher than one-third of the melting point is crucial for the growth of nanowhiskers. Deposition on surfaces with systematically controlled roughness indicates that the surface diffusion of adatoms on the substrate surface is not important for the growth of nanowhiskers and that the atoms are mainly supplied from the vapor directly or from reflection on the surface in front of the growing nanowhiskers. The kinetic growth model that takes into account the GLAD and the reflection agrees with the experimental results.