We observed a scaling behavior during the shadowing growth of isolated Si, Co, Cu, and W nanocolumnar structures on Si substrates using the oblique angle deposition with substrate rotation ͑also known as glancing angle deposition or simply GLAD͒. The width of the isolated columns, W, grew as a function of column length, d, in a power law form, Wϳd p , where p is the growth exponent and was measured to be ϳ0.28-0.34. It is argued that shadowing without diffusion should lead to pϭ0.50 and would cross over to 0.31 if one considers surface diffusion. It is of great interest to determine the mechanisms that would affect the value of p since it is an important factor that would control the shape, final size, and spacing of the isolated nanocolumns eventually produced.

In this paper we report on the morphological evolution of thin films grown by commonly employed deposition techniques, such as sputtering and chemical vapor deposition. In these deposition techniques, an angular distribution of incident particle flux leads to the shadowing effect, which often plays an important role in defining the growth front morphology. We show both by simulations and experiments that a mounded structure can be formed with a characteristic length scale, or "wavelength" , which describes the separation of the mounds. We also show that the temporal evolution of is distinctly different from that of the mound size or lateral correlation length . The wavelength grows as a function of time in a power-law form, ϳ t p , where p Ϸ 0.5 for a wide range of growth conditions, while the mound size grows as ϳ t 1/z , where 1 / z varies depending on growth conditions. The existence of these two length scales and their different growth rates leads to a breakdown of the self-affine and dynamic scaling hypotheses that have been used to describe many surface growth phenomena in the past.

Surfaces with metal oxide nanostructures have gained considerable interest in applications such as sensors, detectors, energy harvesting cells, and batteries. However, conventional fabrication techniques suffer from challenges that hinder wide and effective applications of such surfaces. Most of the metal oxide nanostructure synthesis methods are costly, complicated, non-scalable, environmentally hazardous, or applicable to only certain few materials. Therefore, it is crucial to develop a simple metal oxide nanostructure fabrication method that can overcome all these limitations and pave the way to the industrial application of such surfaces. Here, we demonstrate that a wide variety of metals can form metal oxide nanostructures on their surfaces after simply interacting with hot water. This method, what we call hot water treatment, offers the ability to grow metal oxide nanostructures on most of the metals in the periodic table, their compounds, or alloys by a one-step, scalable, low-cost, and eco-friendly process. In addition, our findings reveal that a “plugging” mechanism along with surface diffusion is critical in the formation of such nanostructures. This work is believed to be of importance especially for researchers working on the growth of metal oxide nanostructures and their application in functional devices.

We report the creation of an unusual simple cubic ␤-phase W͑100͒ nanorods with a pyramidal tip having four ͑110͒ facets using an oblique-angle sputter deposition technique with substrate rotation ͑also known as glancing-angle deposition͒. During the oblique-angle deposition, both ␤-phase W͑100͒ and ␣-phase W͑110͒ islands exist at the initial stages of growth. The ␤-phase W͑100͒ islands grow taller due to the lower adatom mobility on these islands. The taller islands survive in the competition and form isolated nanorods in the later stages of growth. This is in contrast to the sputter deposition at normal incidence, where only the thermodynamically stable bcc ␣-phase W͑110͒ polycrystalline films were formed when the film grows to a certain thickness.

The growth-front roughness of amorphous silicon films grown by dc magnetron sputtering at low pressure has been investigated using atomic force microscopy. The interface width w increases as a power law of deposition time t, wϳt ␤ , with ␤ϭ0.41Ϯ0.01, and the lateral correlation length grows as ϳt 1/z , with 1/z ϭ0.42Ϯ0.02. The roughness exponent extracted from height-height correlation analysis is ␣ϭ0.83Ϯ0.03. None of the known growth models can be used to explain the scaling exponents we obtained. Monte Carlo simulations were carried out based on a re-emission model where incident flux distribution, sticking coefficient, and surface diffusion were accounted for in the growth process. The morphology and the scaling exponents obtained from simulations are consistent with the experimental results. When the surface diffusion