Adsorption on a doped semiconductor surface often induces a gradual formation of a carrier-accumulation layer at the surface. Taking full account of a nonparabolic ͑NP͒ conduction-band dispersion of a narrow-gap semiconductor, such as InAs and InSb, we investigate the evolution of electron states at the surface in an accumulation-layer formation process. The NP conduction band is incorporated into a local-density-functional formalism. We compare the calculated results for the NP dispersion with those for the parabolic ͑P͒ dispersion with the band-edge effective mass. With increase in the accumulated carrier density N S , the accumulated carriers for the NP conduction band start to be more localized in closer vicinity to the surface than those for the P one. As the bottoms of a few lowest subbands drop below the Fermi level one after another with increase in N S , the nonparabolicity begins to have a great influence on the dispersion and the bottom of each of these subbands, particularly on those of the lowest subband. The present work provides a numerical basis for making a quantitative examination of surface electronic excitations in the accumulation-layer formation process.

Arrays of stretchable and transparent electronic sensors realize next-generation skin-conformable wearables and soft robotic skins, which require a high-resolution patternable stretchable conductor. However, the difficulty of simultaneously engineering desirable material properties (i.e., conductivity, stretchability, and patternability) has limited the development of such stretchable electronic materials. Herein, a high-resolution patternable, stretchable, and transparent conducting polymer by decoupled engineering of the material properties is shown. The high conductivity of the conducting polymer is achieved by rationally designing an ionic additive. The high stretchability is realized by matching the mechanical properties of the conducting polymer to the substrate. The developed conducting polymer is then patterned in a resolution less than 10 μm by nanosecond UV laser ablation, which enables the feasible demonstration of stretchable and transparent sensor arrays for touch and strain. The findings in this work will accelerate the development of high-density stretchable sensor arrays and stretchable semiconductor devices.