Although many groups have studied the initial growth stages of various metals, including indium, there is little
information in literature on diameter distributions of indium in relation to film thickness or annealing conditions. This
paper reports island size distributions of thermally evaporated In islands on Si (100) and Si (111) substrates for
nominal film thicknesses ranging from 5 to 50 nm. Because indium has a low melting temperature, and therefore a
high homologous temperature at room temperature, 3-dimensional islands form during deposition with no subsequent
heat treatments needed. Island diameters were calculated using commercial image analysis software in conjunction
with SEM images of the samples. It is found that there is a bimodal island diameter distribution for nominal indium
thicknesses greater than 5 nm. While the diameters of the larger islands increase exponentially with nominal
thickness, those of the smaller islands increase linearly, and therefore more slowly, with nominal thickness. For
nominal thickness of 50 nm, the average diameters of the small and large islands differ by almost an order of
magnitude. Anneal conditions were studied in an attempt to narrow diameter distributions. Samples of each nominal
thickness were annealed at temperatures ranging from 360°C to 550°C and the diameters again measured. The range
of island diameters become narrower with 360°C anneal and volume average island diameter increases by ~30-50%.
This narrowing of the distribution occurs due to smaller islands being absorbed by the larger in a process akin to
Ostwald ripening, which is facilitated by higher surface diffusivities at higher homologous temperatures.
The broadband optical absorption properties of silicon nanowire (SiNW) films fabricated on glass substrates by wet etching and chemical vapor deposition (CVD) have been measured and found to be higher than solid thin films of equivalent thickness. The observed behavior is adequately explained by light scattering and light trapping though some of the observed absorption is due to a high density of surface states in the nanowires films, as evidenced by the partial reduction in high residual sub-bandgap absorption after hydrogen passivation. Finite difference time domain simulations show strong resonance within and between the nanowires in a vertically oriented array and describe the experimental absorption data well. These structures may be of interest in optical films and optoelectronic device applications.
Integration of nanowires onto foreign substrates, and in functional devices, is widely recognized as a significant hurdle to further development of nanosystems based on quasi-one dimensional nanostructures. We describe methods for directly integrating relevant nanostructures on technologically relevant Si substrates using vapor phase synthesis of the nanowires. It is shown that ZnO nanowires may be directly integrated onto Si substrates containing patterned metal lines. Preferential growth from the edge of the metal lines has been achieved. We also show that growth of refractory transition metal carbides is also possible using catalytic growth. The electrical properties of such systems are also discussed. Finally, methods of integrating nanowires vertically on a Si substrate are also described.