The effect of the selective adsorption of pig serum albumin as an antigen on the electrical properties of a carbon nanotube channel field effect transistor on which anti-pig serum albumin was immobilized as an antibody by physisorption in phosphate buffer solution has been investigated. We have succeeded in real-time detection of the adsorption of pig serum albumin on anti-pig serum albumin as a decrease in the conductance of the carbon nanotube channel field effect transistor, by a label-free process.
The application of atomic-force-microscope (AFM) direct patterning to the selective positioning of InAs quantum dots (QDs) on a (100) GaAs substrate has been proposed and experimentally implemented. The AFM direct patterning was used to generate various patterns of several tens of nanometers in size, and InAs QDs were subsequently grown by a metalorganic chemical vapor deposition technique. A nonuniform distribution of the QDs was observed near the patterns. The detailed shape of the QD distribution and the size of the QDs depended on the geometrical properties such as the sidewall angle, the spacing, and the width of the patterns. We have been able to ascertain, through our work, what growth conditions are necessary for QDs’ alignment along the patterns.
A resistless nanostructure patterning technique using tip oscillation of an atomic force microscope (AFM) was systematically investigated. Commercial AFM cantilevers are used to successfully generate patterns as narrow as 10 nm on a GaAs surface, without further sharpening of the tips. Reliable patterns with fully controlled width and depth are achieved by adjusting the feedback gain and the scan speed. This process allows nanometer-scale patterning to be performed simply, and is well suited for nanodevice fabrication.
InAs/GaAs multistacked quantum dot (QD) layers were grown by using molecular beam epitaxy with various numbers of stacking cycles to investigate the shape and the interband transition in the InAs QDs. The appearance of another photoluminescence (PL) peak on InAs/GaAs QDs with more than six stacking cycles originated from the change of the QDs from an isotropic pyramidal shape to an elongated anisotropic pyramidal shape. Dislocation lines along the [1 1 10] direction existing on the InAs/GaAs QDs with more than six stacking cycles were attributed to the existence of excessive strain fields. Scanning transmission electron microscope and atomic force microscope images showed that the QD shape in the [1 1 10] direction was elongated without any remarkable change in the volume of the QDs. These results indicate that the shape of the InAs/GaAs QDs was strongly affected by the number of the stacking cycles and that the appearance of another PL peak is related to the change of the QD shape.
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