Studies of hydrogen diffusion, hydrocarbon adsorption and palladium nanowires on silicon(001) with scanning tunneling microscopy and atom tracking

The design and preliminary microfabrication of a scanning tunneling microscope (STM) has been undertaken. A three-dimensional suspended microelectromechanical system (MEMS) was started to master preliminary micro-processing techniques. The design of an STM weighing 2 × 10−10 kg, consisting of single crystal silicon beams is based on capacitive comb and torsional drives as a means of actuation. The mechanical resonant frequencies of the x, y and z drives are 100 kHz, 100 kHz, and 1MHz, respectively. The microfabrication was performed using single crystal silicon, reactive ion etching, and metallization (SCREAM).; In addition, studies on the silicon (001) surface were performed in three areas: hydrogen diffusion, hydrocarbon adsorption, and selective palladium deposition. The diffusion of hydrogen was measured and compared to deuterium using STM atom tracking. Attempt frequencies and activation energies for diffusion along the dimer row (intrarow) and between the atoms of a single Si dimer (intradimer) are extracted. For intrarow H diffusion, an activation energy of 1.75 ± 0.10 eV and an attempt frequency of 1014.5±0.8 Hz are found. For intradimer H diffusion, an activation energy of 1.01 ± 0.05 eV and a low attempt frequency of 1010.3±0.5 diffusion are also determined.; Alkane and Alkene hydrocarbons were deposited on Si(001). The alkanes were observed to have low sticking coefficients in addition to no regularized adsorption morphology. Alkenes had high sticking probabilities. Anthracene and thiophene (C₄H₄S) were found to have high sticking coefficients in addition to adsorbing along dimer rows. STM images support the theoretical prediction that thiophene adsorbs atop, to one side of the dimer rows. We find that the diffusion of thiophene rules out Si-Si dimer bonds breaking upon C₄H₄S adsorption. The annealing of naphthalene induces a c(4 x 4) phase of Si(001) at 1000K, and SiC cluster formation near BOOK.; We demonstrate selective physical vapor deposition of palladium to form nanostructures on Si(001) using STM lithography with an atomic hydrogen resist. The selectivity of the PVD process is due to the longer diffusion length of Pd on the hydrogen resist layer than on clean Si(001). Further, the selectivity is enhanced at elevated temperatures and a palladium silicide is formed around 1000K.