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We have observed the native oxide decomposition and local oxide growth on 6H-silicon carbide (0001) surface induced by atomic force microscopy (AFM). When the biased AFM probe was scanned over surface areas, native oxide was decomposed and assembled into protruded lines. The decomposition is accompanied by simultaneous graphitization of the scanned areas, leading to metal–semiconductor contact as evidenced in I–V characteristics. When the probe was immobilized and longer bias duration applied, direct oxidation of silicon carbide (SiC) surface was achieved. The dielectrical properties of AFM oxide on SiC were also investigated in terms of interface barrier height.

A 6×6 reconstruction consisting of a silicon-rich phase has been observed on 6H–SiC (0001) after annealing a silicon-enriched 3×3 6H–SiC (0001) surface at 900 °C. Our results show that the 6×6 reconstruction obtained is a long-range reconstruction and not a psuedoperiodic structure due to incommensurately adsorbed graphite honeycombs as suggested previously. We propose that the 6×6 structure arises from the absence of consecutive tetrahedral clusters in a tetrahedral cluster array with 3×3 periodicity. Annealing the 6×6 structure further at 1200 °C results in a carbon-rich 6√3×6√3R30 structure.

This letter reports the negative differential resistance (NDR) behavior of perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride films induced by aggregate formation in the film. It is observed that aggregate-states in the energy gap can by-pass the common charge conduction mode, and electron injection, trapping, and conduction through these states lead to the NDR characteristic. The rate-dependence of NDR is discussed in terms of the transit time and lifetime of the aggregates-states electrons. The quenching of NDR by photoillumination is also observed, and is attributed to the saturation of aggregates-states by photoelectrons.

This work reports a mechanism of negative differential resistance (NDR) observed for perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) films. The NDR is based on electron injection and extraction at the metal/PTCDA interface, and is governed by the joint effect of electronic and ionic components. Consequently, the NDR behavior exhibits a monotonous dependence on the voltage scan rate, and the number of NDR peaks is also sensitive to the work function of metal electrodes. The results provide further understanding on the diverse manifestation of NDR, and would be useful in organic electronic applications.

A probe-based nano-oxidation method for enhanced vertical oxide growth on silicon is presented. The technique involves cycling the tip biases between positive and negative polarities to produce high-aspect-ratio nano-oxides. Enhanced oxidation was observed to take place in the positive tip bias region as opposed to the negative tip voltage required for anodic oxidation. A model based on interface space charge accumulation and neutralization, OH− reactant mobilization, and diffusion is proposed to account for the oxidation enhancement observed under positive tip voltages. The proposed model is analogous to the transient charge pump effect which is at work when the polarity of a capacitor is switched. The results reveal the dynamical behavior of nano-oxidation under nonstatic fields which can be harnessed for fabricating oxide nanostructures with improved aspect ratios.

We report the creation of polymeric structures by atomic force microscopy (AFM) probe induced electrohydrodynamic (EHD) instability and nanofluidic flow. By biasing the AFM probe in a high field regime, single conical structure was produced on poly(methylmethacrylate) due to the initiation of strong EHD instability in the locally heated polymer melts. The pattern formation is dominated by the interplay of polymer EHD motion, polymer ablation, and AFM tip repulsion. The dependence of cone formation probability on the bending of AFM cantilevers with different stiffness was also discussed.

We report a comparative study on the chemical and dielectrical properties of ultrathin oxides grown by atomic force microscopy (AFM) and scanning electron beam (SEB) techniques. Oxide grown by AFM (AFM oxide) shows preferential etching as compared to oxide grown by SEB (SEB oxide). The structural and chemical features of these oxides were probed using time-of-flight secondary ion mass spectrometry (TOF-SIMS) time profiling. It was found that AFM oxide is richer in Si–H and Si–OH content, while SEB oxide is oxygen rich and relatively dense in structure. The dielectric strength of AFM and SEB oxides were further evaluated by conducting AFM (c-AFM). The current–voltage characteristics and dielectric breakdown probability of these oxides were compared. The correlation between Si–H and Si–OH site formation and its impact on the chemical and dielectrical stability of AFM and SEB oxides was discussed.

We report an investigation on the stress-induced breakdown (BD) in ultrathin oxide grown by atomic force microscopy (AFM oxide). A conducting atomic force microscopy (c-AFM) technique was employed to stress the AFM oxide and examine its BD behavior. It was found that thermal annealing has a strong impact on the dielectric strength of AFM oxide. The stress-induced trap generation probability, Pt, could be reduced by ∼50% after annealing the oxide at elevated temperatures. Such a thermal effect is related to the local structural relaxation and trap state minimization in AFM oxide upon annealing. The spatially resolved current images allow a microscopic diagnosis of the distribution of BD sites: isolated single BD spots and laterally propagated BD areas were observed in an oxide dot. Soft and hard breakdown sites were also distinguished on the current images.