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We present "design rules" for the selection of molecules to achieve electronic control over semiconductor surfaces, using a simple molecular orbital model. The performance of most electronic devices depends critically on their surface electronic properties, i.e., surface band-bending and surface recombination velocity. For semiconductors, these properties depend on the density and energy distribution of surface states. The model is based on a surface state-molecule, HOMO-LUMO-like interaction between molecule and semiconductor. We test it by using a combination of contact potential difference, surface photovoltage spectroscopy, and time-and intensity-resolved photoluminescence measurements. With these, we characterize the interaction of two types of bifunctional dicarboxylic acids, the frontier orbital energy levels of which can be changed systematically, with air-exposed CdTe, CdSe, InP, and GaAs surfaces. The molecules are chemisorbed as monolayers onto the semiconductors. This model explains the widely varying electronic consequences of such interaction and shows them to be determined by the surface state energy position and the strength of the molecule-surface state coupling. The present findings can thus be used as guidelines for molecule-aided surface engineering of semiconductors.

CuSn alloy nanowires capped with Ni were prepared using sequential electrodeposition of nickel and a copper/tin bronze alloy into nanoporous alumina templates. The liberated nanowires were suspended in solvents and their behavior monitored using optical microscopy. The nanowires were oriented and spun in circles as "nano stirbars" using applied magnetic fields. These segmented nanowires were also trapped between magnetized Ni stripes, demonstrating that nonmagnetic metallic nanowires can be manipulated and positioned by capping them with magnetic ends.A wide variety of one-dimensional nanostructures displaying useful properties has been fabricated in recent years. 1 Carbon nanotubes, semiconductor nanowires, and metallic nanowires are of interest for their optical and electronic properties. Applications explored to date include nanoelectronic circuits, 2,3 ultraviolet lasers, 4 chemical sensors, 5 and optical switches. 6 To incorporate nanowires into devices, it is critically important to be able to control their motion and position. Work has begun in this area using a variety of alignment techniques, including microfluidic channels, 7 liquid crystal templates, 8 and patterned surfaces. 9 Electric fields have been used to control the position of semiconductor 10 and metallic nanowires. 11 Recently, the alignment of nickel nanowires has been controlled using magnetic fields. 12 In this paper we report on a general method for the manipulation of nonmagnetic metal nanowires that are prepared by electrodeposition in nanoporous membranes. Specifically, we show that by preparing nonmagnetic CuSn alloy nanowires so that they are capped with Ni ends, magnetic fields may be used to orient and spin the nanowires. This method of nanowire control can be applied in principle to any template-synthesized nanowire system containing conductive material.The synthetic technique employed in this work is the template method in which nanowires are made by filling the nanoscale pores of alumina or polycarbonate membranes. 13,14 This is an attractive preparative route for two reasons: First, approximately one billion nanowires that are relatively uniform in length and diameter can be made simultaneously.Second, subsequent dissolution of the template easily liberates the nanowires for study and application in nanoscale devices. The technique has been used to make nanowires from a variety of materials, including pure metals, 15 semiconductors, 16 multilayer GMR structures, 17,18 superconductors, 19,20 conductive polymers, 21 hydrogels, 22 and magnetic metals. 23,24 Moreover, the template method allows for precise control over the composition of the nanowires, as composition can be varied along the length and diameter of the wire. 22,25 When electrodeposition is used to fill the pores, metallic stripes can be formed by using a solution containing two or more metal ions and varying the applied potential, 17 or by exchanging different electrolyte solutions sequentially. 26 Such segmented nanowires have demonstrated remarkable abilities as GM...

In this study, a series of nanoindentations was made on NiTi shape memory alloy thin films at millinewton loads with a Berkovich indenter. Mapping of the indentation topography using atomic force microscopy reveals direct evidence that the thermally induced martensitic transformation of these films allows for partial indent recovery on the nanoscale. Indeed, recovery is nearly complete at indentation depths of less than 100 nm. A hemispherical cavity model is presented to predict an upper limit to shape memory recovery of sharp indentations.