The patterning of polysilane films is performed by means of the contact-mode-Scanning Probe Microscope(SPM) lithography technique. Both a carbon nanotube tip and a gold-coated Si tip are used. The polysilane film is directly patterned or grooved when the tip is negatively biased. It is considered that the grooves are fabricated by the scission of Si-Si bonds and volatilization of the species due to the emanating of electrons from the scanning tip. Compared with gold-coated Si tips, carbon nanotube tips produce narrower grooves with a higher scan speed and have a longer lifetime. The maximum ratio of groove depth to width can be obtained at a speed as high as 20 µm/s when using the carbon nanotube tip.

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Nanolithography of polysilane films is performed by means of a tapping-mode-scanning probe microscope (SPM) equipped with a carbon nanotube tip. The tapping mode enables us to perform finer lithography than that by the contact mode. Electrons injected from the tip directly groove the polysilane film. A constant current operation is more stable in the tapping-mode lithography than a constant bias voltage operation. The mechanism of direct lithography is discussed on the basis of the model that the excess electrons in the Si backbone break Si-Si bonds. Fig. 6. Illustration explaining the mechanism of lithography in polysilane films. The injection of excess electrons into the Si backbone breaks Si-Si bonds to produce small fragments which are volatile. Si Si

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The effect of nanomaterials on biological reactions has received much attention. We report herein that silicon nanowires (SiNWs) inhibit the polymerase chain reaction (PCR). The inhibitory effect was found to be concentration-dependent, with a minimum inhibitory concentration of about 0.4 mg ml −1 . DNA polymerase, restriction endonucleases, lysozyme and horseradish peroxidase maintained their bioactivities after exposure to SiNWs. Also the interaction of SiNWs with primers and dNTP did not lead to decreased PCR yield. Compared to primers and dNTP, template DNA showed 4.7-10.5-fold greater adsorption on SiNWs. Template bound to SiNWs was ineffective in the PCR, whereas addition of free template to the PCR system increased the yield. The results of this work suggest that the inhibitory effect of SiNWs on the PCR was due to the selective adsorption of double-stranded DNA on SiNWs, thereby decreasing the availability of template for the reaction.