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A double-layer nanostructure comprising amorphous Si nanograss on top of Si nanofrustums (NFs) with a total height of 680 nm exhibits ultralow reflection. Almost near-unity absorption and near-zero reflectance result in this layered nanostructure, over a broad range of wavelengths and a wide range of angles of incidence, due to the low packing density of a-Si and the smooth transition of the refractive index from the air to the Si substrate across both the nanograss and NF layers.

Plasma-made nanostructures show outstanding potential for applications in nanotechnology. This paper provides a concise overview on the progress of plasma-based synthesis and applications of silicon nanograss and related nanostructures. The materials described here include black silicon, Si nanotips produced using a self-masking technique as well as self-organized silicon nanocones and nanograss. The distinctive features of the Si nanograss, two-tier hierarchical and tilted nanograss structures are discussed. Specific applications based on the unique features of the silicon nanograss are also presented.

Thin‐film transistors (TFTs) grown on a flexible glass substrate using single‐crystal‐like germanium (Ge) channel to simultaneously achieve high carrier mobility, high performance characteristics, mechanical flexibility, and cost‐effective large‐area manufacturing are reported. High‐crystalline‐quality materials of biaxially textured CeO2 deposited at room temperature by ion‐beam‐assisted deposition followed by single‐crystal‐like Ge epitaxially grown at 550 °C by plasma‐enhanced chemical vapor deposition on an amorphous substrate are developed. p‐type Ge with {111} surface shows well‐aligned grains in both out‐of‐plane and in‐plane directions, as characterized by reflection high‐energy electron diffraction, X‐ray diffraction, and Raman spectroscopy. The material structures are fabricated to transistor devices with top‐gate geometry. The devices (channel width and length = 80 and 14 μm) exhibit performance characteristics with on/off ratio of ≈106, a field‐effect mobility of ≈105 cm2 V−1 s−1, and saturation current levels of ≈3.5 mA, which are significantly higher than performance metrics of other state‐of‐the‐art TFTs based on amorphous Si, organic semiconductors, and semiconducting oxides. This development can open a new avenue for next‐generation TFTs beyond the display applications.

This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.