We have fabricated graphene-silicon Schottky diodes by depositing mechanically exfoliated graphene on top of silicon substrates. The resulting current–voltage characteristics exhibit rectifying diode behavior with a barrier energy of 0.41 eV on n-type silicon and 0.45 eV on p-type silicon at the room temperature. The I–V characteristics measured at 100, 300, and 400 K indicate that temperature strongly influences the ideality factor of graphene–silicon Schottky diodes. The ideality factor, however, does not depend strongly on the number of graphene layers. The optical transparency of the thin graphene layer allows the underlying silicon substrate to absorb incident laser light and generate a photocurrent. Spatially resolved photocurrent measurements reveal the importance of inhomogeneity and series resistance in the devices.

Graphene-Silicon Schottky Diodes

Characterization of a Mo/ZSM-5 catalyst for the conversion of methane to benzene

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A processing chamber may be effectively cleaned by a remote plasma flowed through the chamber in a direction opposite to the direction of gas flowed during wafer processing. Specifically, the remotely generated plasma may be introduced directly into the chamber through a processing gas exhaust or other port, and then be exhausted from the chamber by traveling through the gas distribution shower head to the foreline. In one embodiment of the present invention, this reverse flow of remote cleaning plasma is maintained for the duration of the chamber cleaning step. In an alternative embodiment, the direction of flow of the remote cleaning plasma through the chamber is alternated between this reverse flow and a conventional forward flow.

Backflush chamber clean

Selective localization of active proteins to patterns or specific sites is important for development of biosensors, bioMEMS, tissue engineering, and basic proteomic research. We present a flexible technique for selectively patterning bioactive proteins with nanoscale resolution using nanoimprint lithography and fluoropolymer surface passivation, and exploiting the specificity of the biotin/streptavidin linkage. This technique achieves high throughput reproducible nanoscale protein patterns with high selectivity and retained biofunctionality, as demonstrated by interactions between patterned antibodies and their antigen.

Nanoscale protein patterning by imprint lithography

The chemical dry etching of silicon nitride (Si3N4)and silicon nitride (SiO2) in a downstream plasma reactor using CF4, O2, and N2 has been investigated. A comparison of the Si3N4 and SiO2 etch rates with that of polycrystalline silicon shows that the etch rates of Si3N4 and SiO2 are not limited by the amount of fluorine arriving on the surface only. Adding N2 in small amounts to a CF4/O2 microwave discharge increases the Si3N4 etch rate by a factor of 7, but leaves the SiO2 etch rate unchanged. This enables etch rate ratios of Si3N4 over SiO2 of 10 and greater. The Si3N4 etch rate was investigated with respect to dependence of tube length, tube geometry, and lining materials. Argon actinometry has shown that the production of F atoms in the plasma is not influenced by the addition of N2 to the discharge. Mass spectrometry shows a strong correlation between the Si3N4 etch rate and the NO concentration. X‐ray photoelectron spectra of the silicon nitride samples obtained immediately after the etching proces...

Chemical dry etching of silicon nitride and silicon dioxide using CF4/O2/N2 gas mixtures

A highly selective dry etching process for the removal of silicon nitride (Si3N4) layers from silicon and silicon dioxide (SiO2) is described and its mechanism examined. This new process employs a remote O2/N2 discharge with much smaller flows of CF4 or NF3 as a fluorine source as compared to conventional Si3N4 removal processes. Etch rates of Si3N4 of more than 30 nm/min were achieved for CF4 as a source of fluorine, while simultaneously the etch rate ratio of Si3N4 to polycrystalline silicon was as high as 40, and SiO2 was not etched at all. For NF3 as a fluorine source, Si3N4 etch rates of 50 nm/min were achieved, while the etch rate ratios to polycrystalline silicon and SiO2 were approximately 100 and 70, respectively. In situ ellipsometry shows the formation of an approximately 10-nm-thick reactive layer on top of the polycrystalline silicon. This oxidized reactive layer suppresses etching reactions of the reactive gas phase species with the silicon.

Highly selective etching of silicon nitride over silicon and silicon dioxide

The etching of silicon nitride (Si3N4) and silicon dioxide (SiO2) in the afterglow of NF3 and NF3/O2 microwave discharges has been characterized. The etch rates of both materials increase approximately linearly with the flow of NF3 due to the increased availability of F atoms. The etch rate of Si3N4 is enhanced significantly upon O2 injection into the NF3 discharge for O2/NF3 ratios of 0.3 and higher, whereas the SiO2 etch rate is less influenced for the same flow ratios. X-ray photoelectron spectroscopy of processed Si3N4 samples shows that the fluorine content of the reactive layer, which forms on the Si3N4 surface during etching, decreases with the flow of O2, and instead oxidation and nitrogen depletion of the surface occur. The oxidation of the reactive layer follows the same dependence on the flow of O2 as the etch rate. Argon actinometry and quadrupole mass spectrometry are used to identify reactive species in the etching of both materials. The atomic fluorine density decreases due to dilution as O...

Remote plasma etching of silicon nitride and silicon dioxide using NF3/O2 gas mixtures

The remote plasma chemical dry etching of polycrystalline silicon was investigated using various CF4/O2/N2 gas compositions The effects of O2 and N2 addition on the etch rate and surface chemistry were established Admixing O2 to CF4 increases the gas phase fluorine density and increases the etch rate by roughly sevenfold to a maximum at an O2/CF4 ratio of 015 The addition of small amounts of N2 (N2/CF4=005) can again double this etch rate maximum Strong changes in surface chemistry were also seen as a result of N2 addition to CF4/O2 Real-time ellipsometry and atomic force micro-roughness measurements reveal that nitrogen addition at low O2/CF4 ratios leads to the smoothing of surfaces, but to increased oxidation at high O2/CF4 ratios Based on etch rate data and gas phase species analysis, we propose that NO plays an important role in the overall etching reaction Variable tube lengths separated the reaction chamber from the discharge These tubes were lined with either quartz or Teflon liners In 

Role of N2 addition on CF4/O2 remote plasma chemical dry etching of polycrystalline silicon

Pattern transfer by plasma-based etching is one of several key processes required for fabricating silicon-based integrated circuits. We present a brief review of elementary plasma-etching processes...

B. E. E. Kastenmeier

Papers

Chemical dry etching of silicon nitride and silicon dioxide using CF4/O2/N2 gas mixtures

Highly selective etching of silicon nitride over silicon and silicon dioxide

Remote plasma etching of silicon nitride and silicon dioxide using NF3/O2 gas mixtures

Role of N2 addition on CF4/O2 remote plasma chemical dry etching of polycrystalline silicon

Surface science issues in plasma etching