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Silicon on insulator (SOI)-based transistors gated by nanogranular SiO2 proton conducting electrolytes were fabricated to mimic synapse behaviors. This SOI-based device has both top proton gate and bottom buried oxide gate. Electrical transfer properties of top proton gate show hysteresis curves different from those of bottom gate, and therefore, excitatory post-synaptic current and paired pulse facilitation (PPF) behavior of biological synapses are mimicked. Moreover, we noticed that PPF index can be effectively tuned by the spike interval applied on the top proton gate. Synaptic behaviors and functions, like short-term memory, and its properties are also experimentally demonstrated in our device. Such SOI-based electronic synapses are promising for building neuromorphic systems. [ABSTRACT FROM AUTHOR]

Tubular optical microcavities have been fabricated by releasing prestressed SiO/SiO2 bilayer nanomembranes from polymer sacrificial layers, and their geometrical structure is well controlled by defining the shape of nanomembranes via photolithography. Optical measurements at room temperature demonstrate that resonant modes of microtubular cavities rolled up from circular shapes can be tuned in peak energy and relative intensity along the tube axes compared to those from square patterns. The resonant modes shift to higher energy with decreasing number of tube wall rotations and thickness, which fits well to finite-difference time-domain simulations. Polarization resolved measurements of the resonant modes indicate that their polarization axes are parallel to the tube axis, independent of the polarization of the excitation laser. [ABSTRACT FROM AUTHOR]

Unique structured SiOxNy-capped Si nanowire arrays were fabricated via electroless metal deposition on α-SiOxNy-covered Si wafer in ionic silver HF solution through selective chemical etching. A self-assembled localized microscopic electrochemical cell model and a diffusion-limited aggregation process are associated with the formation of the SiOxNy-capped Si nanowire arrays. An enhanced blue photoluminescence band has been recorded. Emission and excitation spectral analyses suggest that generation of photoexcited carriers takes place mainly in the quantum confined Si nanowires, whereas their radiative recombination occurs in the Si–N binding states of SiOxNy nanocaps. [ABSTRACT FROM AUTHOR]

Pre-stressed multi-layer nanomembranes are rolled-up into a microtube in order to tune the strain applied to the contained coupled GaAs quantum wells. Additional GaAs/AlAs adjusting layers were deposited on the top of the nanomembrane to alter the thickness/stiffness of the to-be-rolled nanomembrane. In this way, microtubes with an adjustable diameter and strain are possible from a single initial grown sample. The internal strain state in the microtube affects the energy levels of the quantum wells and their coupling, which can be probed sensitively by photoluminescence. We measure different strain relaxation in rolled-up nanomembranes which we explain using a gradual change of the longitudinal relaxation as the distance of the nanomembrane from the etching front varies. [ABSTRACT FROM AUTHOR]

SiO[sub 2]/Ge:SiO[sub 2]/SiO[sub 2] sandwiched structure was fabricated for exploring efficient light emission. After annealed in N[sub 2] (O[sub 2]<1%), this structure shows three photoluminescence (PL) bands at 293, 395, and 780 nm. The intensity of the 395 nm band is largely enhanced in comparison with that from the monolayered Ge:SiO[sub 2] film. Spectral analyses suggest that the three PL bands originate from S[sub 1]→S[sub 0], T[sub ∑](T[sub ∏])→S[sub 0], and T[sub ∏][sup ′]→S[sub 0] optical transitions in GeO color centers, respectively. The improvement of the GeO density resulting from the confinement on Ge diffusion is responsible for the enhanced ultraviolet PL. This structure is expected to have important applications in optoelectronics. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]