An areal density of 1.6 Tbits/in. 2 has been achieved by anodically oxidizing titanium with the atomic force microscope ͑AFM͒. This density was made possible by ͑1͒ single-wall carbon nanotubes selectively grown on an AFM cantilever, ͑2͒ atomically flat titanium surfaces on ␣-Al 2 O 3 ͑1012͒, and ͑3͒ atomic scale force and position control with the tapping-mode AFM. By combining these elements, 8 nm bits on 20 nm pitch are written at a rate of 5 kbit/s at room temperature in air.

This paper proposes an obliquely aligned InN nanorod array to maximize nanorod deformation in the application of nanopiezotronics. The surface-dependent piezotronic I-V characteristics of the InN nanorod array with exposed polar (0002) and semipolar ( ̅1102) planes were studied by conductive atomic force microscopy. The effects of the piezopotential, created in the InN under straining, and the surface quantum states on the transport behavior of charge carriers in different crystal planes of the InN nanorod were investigated. The crystal plane-dependent electron density in the electron surface accumulation layer and the strain-dependent piezopotential distribution modulate the interfacial contact of the Schottky characteristics for the (0002) plane and the quasi-ohmic behavior for the ( ̅1102) plane. Regarding the piezotronic properties under applied forces, the Schottky barrier height increases in conjunction with the deflection force with high current density at large biases because of tunneling. The strain-induced piezopotential can thus tune the transport process of the charge carriers inside the InN nanorod over a larger range than in ZnO. The quantized surface electron accumulation layer is demonstrated to modulate the piezopotential-dependent carrier transport at the metal/InN interfaces and become an important factor in the design of InN-based piezotronic devices and nanogenerators.

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Piezoelectric materials such as ZnO and III-nitride are gaining increasing attention for their energy-related applications, including high-brightness light-emitting diodes (LEDs), fullspectrum solar cells, and nanogenerators. Because of the inconvenience of using chemical batteries to power wireless sensors, harvesting energy from ambient mechanical movements in variable and uncontrollable environments is an effective method of powering wireless mobile electronics for a wide range of applications in everyday life. The operating principle of a nanowire-based nanogenerator involves the unique coupling of the piezoelectric and semiconducting properties and the gating effect of the Schottky barrier formed between metal tips and semiconductor nanomaterials. Consequently, nanogenerators convert mechanical energy from ambient movement into electricity that can be used to power nanodevices without batteries. Researchers have made great progress in developing piezoelectric nanogenerators based on II-VI compound semiconductor nanomaterials such as ZnO, [ 1 , 2 ] ZnS, [ 3 ] and CdS, [ 4 ] which have great potential for the integration of piezotronics and nanogenerators. Recent efforts to enhance nanogenerator effi ciency have focused on materials with higher piezoelectric coeffi cients, including poly(vinylidene fl uoride) (PVDF) nanofi bers, [ 5 ] BaTiO 3 thin fi lms, [ 6 ] and lead zirconate titanate (PZT) nanofi bers.

The Taiyuan formation limestone water in the Huaibei coalfield is not only the water source for coal mining, but also the water source for industry and agriculture in mining areas. Its hydrogeochemical characteristics and water quality are generally concerning. In this paper, conventional ion tests were carried out on the Taiyuan formation limestone water of 16 coal mines in the Sunan and Linhuan mining areas of the Huaibei coalfield. Piper trigram, Gibbs diagram and an ion scale coefficient map were used to analyze the hydrogeochemical characteristics of the Taiyuan formation limestone water. The water quality was evaluated in a fuzzy comprehensive manner. The results show that the main cation and anion contents in the Taiyuan formation limestone water were Na+ > Mg2+ > Ca2+ > K+, SO42− > HCO3− > Cl−. There were differences in the hydrogeochemical types of the Taiyuan formation limestone water in the two mining areas; HCO3-Na type water was dominant in the Sunan mining area and SO4·Cl-Na type water was dominant in the Linhuan mining area. The chemical composition of the Taiyuan formation limestone water is mainly affected by the weathering of the rock and is related to the dissolution of the evaporated salt and the weathering of the silicate. The fuzzy comprehensive evaluation results show that the V-type water accounts for a large proportion of the Taiyuan formation limestone water in the study area and the water quality is poor. This study provides a basis for the development and utilization of the Taiyuan formation limestone water and water environmental protection in the future.