Graphene shows promise as a future material for nanoelectronics owing to its compatibility with industry-standard lithographic processing, electron mobilities up to 150 times greater than Si and a thermal conductivity twice that of diamond. The electronic structure of graphene nanoribbons (GNRs) and quantum dots (GQDs) has been predicted to depend sensitively on the crystallographic orientation of their edges; however, the influence of edge structure has not been verified experimentally. Here, we use tunnelling spectroscopy to show that the electronic structure of GNRs and GQDs with 2-20 nm lateral dimensions varies on the basis of the graphene edge lattice symmetry. Predominantly zigzag-edge GQDs with 7-8 nm average dimensions are metallic owing to the presence of zigzag edge states. GNRs with a higher fraction of zigzag edges exhibit a smaller energy gap than a predominantly armchair-edge ribbon of similar width, and the magnitudes of the measured GNR energy gaps agree with recent theoretical calculations.

The scanning tunneling microscope has been used to desorb hydrogen from hydrogen-terminated silicon (100) surfaces. As a result of control of the dose of incident electrons, a countable number of desorption sites can be created and the yield and cross section are thereby obtained. Two distinct desorption mechanisms are observed: (i) direct electronic excitation of the Si-H bond by field-emitted electrons and (ii) an atomic resolution mechanism that involves multiple-vibrational excitation by tunneling electrons at low applied voltages. This vibrational heating effect offers significant potential for controlling surface reactions involving adsorbed individual atoms and molecules.

Chemical vapor deposition of graphene on Cu often employs polycrystalline Cu substrates with diverse facets, grain boundaries (GBs), annealing twins, and rough sites. Using scanning electron microscopy (SEM), electron-backscatter diffraction (EBSD), and Raman spectroscopy on graphene and Cu, we find that Cu substrate crystallography affects graphene growth more than facet roughness. We determine that (111) containing facets produce pristine monolayer graphene with higher growth rate than (100) containing facets, especially Cu(100). The number of graphene defects and nucleation sites appears Cu facet invariant at growth temperatures above 900 °C. Engineering Cu to have (111) surfaces will cause monolayer, uniform graphene growth.

Nanoscale patterning of the hydrogen terminated Si(100)-2×1 surface has been achieved with an ultrahigh vacuum scanning tunneling microscope. Patterning occurs when electrons field emitted from the probe locally desorb hydrogen, converting the surface into clean silicon. Linewidths of 1 nm on a 3 nm pitch are achieved by this technique. Local chemistry is also demonstrated by the selective oxidation of the patterned areas. During oxidation, the linewidth is preserved and the surrounding H-passivated regions remain unaffected, indicating the potential use of this technique in multistep lithography processes.

We use scanning tunneling microscopy and spectroscopy to examine the electronic nature of grain boundaries (GBs) in polycrystalline graphene grown by chemical vapor deposition (CVD) on Cu foil and transferred to SiO(2) substrates. We find no preferential orientation angle between grains, and the GBs are continuous across graphene wrinkles and SiO(2) topography. Scanning tunneling spectroscopy shows enhanced empty states tunneling conductance for most of the GBs and a shift toward more n-type behavior compared to the bulk of the graphene. We also observe standing wave patterns adjacent to GBs propagating in a zigzag direction with a decay length of ~1 nm. Fourier analysis of these patterns indicates that backscattering and intervalley scattering are the dominant mechanisms responsible for the mobility reduction in the presence of GBs in CVD-grown graphene.

We report experimental results that replacing hydrogen with deuterium during the final wafer sintering process greatly reduces hot electron degradation effects in metal oxide semiconductor transistors due to a new giant isotope effect. Transistor lifetime improvements by factors of 10-50 are observed. A plausible physical theory suggests that the benefits of deuterium use may be general and also applicable to other areas of semiconductor device processing and fabrication.

One potential application of molecular nanotechnology is the integration of molecular electronic function with advanced silicon technology. One step in this process is the tethering of individual molecules at specific locations on silicon surfaces. This paper reports the fabrication of arrays of individual organic molecules on H-passivated Si(100) surfaces patterned with an ultrahigh vacuum scanning tunnelling microscope (STM). Feedback controlled lithography (FCL) is used to create templates of individual silicon dangling bonds. Molecules introduced in the gas phase then spontaneously assemble onto these atomic templates. Norbornadiene (NBE), copper phthalocyanine (CuPc), and C 60 molecular arrays have been made by this technique and studied by STM imaging and spectroscopy. Both NBE and CuPc molecules appear as depressions in empty states images, whereas in filled states images they are nearly indistinguishable from Si dangling bonds. Furthermore, the fourfold symmetry and central copper atom of CuPc are clearly observed at positive sample bias. Spatial tunnelling conductance maps of CuPc illustrate charge transfer from the surrounding substrate when the molecule is bound to the surface via its central copper atom. On the other hand, when the CuPc molecule interacts with the substrate via an outer benzene ring, molecular rotation is observed. C 60 molecules display intramolecular structure in topographic images and spectroscopic data. The local density of states of C 60 clearly shows the location of the lowest unoccupied molecular orbital, which suggests that the highest occupied molecular orbital is located within 0.3 eV of the fermi level.

A cryogenic UHV scanning tunneling microscope has been used to study the electron stimulated desorption of hydrogen and deuterium from Si(100) surfaces at 11 K. A strong isotope effect is observed, as seen previously at room temperature. Above ϳ5 eV, the desorption yields for H and D are temperature independent, while in the tunneling regime, below 4 eV, H is a factor of ϳ300 easier to desorb at 11 than at 300 K. This large temperature dependence is explained by a model that involves multiple vibrational excitation and takes into account the increase of the Si-H(D) vibrational lifetime at low temperature. [S0031-9007(97)