Adaptation is the most common and basic feature of living systems, which gives species or individuals a survival advantage. In particular, visual adaptation can enable organisms with a clearer understanding of the real world, thereby avoiding potential harm, which is vital for the life activities of organisms. However, current adaptive devices based on logic circuits are still facing the great challenges for large-scale integration and limited bionic functions. Therefore, the hardware impleofmentation of biological visual adaptability through the emerging photoelectric devices may provide a great opportunity for the bionic systems facing complex environments. Here, a novel adaptive device based on a mixed-dimensional van der Waals heterostructure is fabricated by using a gate-modulated 0D-CsPbBr 3-quantum-dots/2D-MoS 2 heterostructure. The device has superior electric adaptabilities and excellent optical absorption abilities owing to its special energy-band structure. The key characteristics of biological adaptation, such as accuracy, sensitivity, inactivation, and desensitization behaviors, are successfully emulated in the device based on the unique trapping-detrapping mechanism. Most importantly, with a photoelectric synergy approach, the fascinating visual adaptation function based on an environment-adjustable threshold is finally demonstrated. These results indicate that the proposed device may be very promising for the future applications of artificial visual systems and intelligent bionic robots.
A room-temperature photoluminescence (PL) study of amorphous nonstoichiometric silicon nitride (SiNX) films prepared under low temperature is reported. PL peak position can be tuned from 1.90 to 2.90 eV by adjusting the film composition. The luminescence lifetime is within the nanosecond range. The dependence of the PL lifetime on the emission energy suggests that band tail states are involved in the thermalization and recombination of photon-generated carriers. This is further supported by the correlation between the optical band gap, the PL peak energy, and the width of the PL spectrum. We propose that optical transitions among band tail states are the main light emission mechanisms.
Electrically activated doping of boron (B) atoms into the Si-nanocrystals (Si-NCs) embedded silicon oxide film is achieved by co-sputtering technique following with the annealing treatment. The evolution of the size, the shape, and the density of Si-NCs with the doping of B atoms is investigated. The observation of x-ray photoelectron spectroscopy of Si 2p and B 1s and the decrease in lattice spacing of Si (111) plane suggest that B atoms are doped into Si-NCs. The activated doping is confirmed by the Fano effect of the micro-Raman spectra for Si-NCs and the drastic decrease of the sheet resistance.
We report on the characterization of thermally induced interdiffusion in InAs/GaAs quantum-dot superlattices with high-resolution x-ray diffraction and photoluminescence techniques. The dynamical theory is employed to simulate the measured x-ray diffraction rocking curves of the InAs/GaAs quantum-dot superlattices annealed at different temperatures. Excellent agreement between the experimental curves and the simulations is achieved when the composition, thickness, and stress variations caused by interdiffusion are taken in account. It is found that the significant In–Ga intermixing occurs even in the as-grown InAs/GaAs quantum dots. The diffusion coefficients at different temperatures are estimated.
Silicon-rich silicon nitride (SiN X ) films have attracted enormous interests due to their promising luminescence properties and well compatibility with current CMOS technique. In this short review, the fabrication process of SiN X was addressed as well as their chemical composition and structure. The optical properties and future applications of the light emitting devices (LEDs) were also discussed. By analyzing the carrier conduction and combination mechanisms, electroluminescence (EL) intensity of LEDs was greatly improved through the following approaches: passivation of the interfacial states between SiN X films and Si substrates through NH 3 plasma pre-treatment and post-annealing process; the balance of carrier injection via SiO 2 electron accelerating layer; increase of the carrier-injection efficiency and light extraction efficiency and the enhancement of radiative recombination efficiency by surface plasmon.
A dual-wavelength common-path digital holographic microscopy based on a single parallel glass plate is presented to achieve quantitative phase imaging, which combines the dual-wavelength technique with lateral shearing interferometry. Two illumination laser beams with different wavelengths (λ1=532 nm and λ2=632.8 nm) are reflected by the front and back surfaces of the parallel glass plate to create the lateral shear and form the digital hologram, and then the hologram is reconstructed to obtain the phase distribution with a synthetic wavelength Λ=3339.8 nm. The experimental configuration is very compact, with the advantages of vibration resistance and measurement range extension. The experimental results of the laser-ablated pit, groove, and staircase specimens show the feasibility of the proposed configuration.
The ultra-thin body and ultra-thin buried-oxide (UTBB) Germanium-on-Insulator (GeOI) substrates have been fabricated by direct wafer bonding and polishing techniques. The Ge and BOX layer thicknesses are as thin as 9 and 13 nm, respectively. The UTBB GeOI substrates exhibit superior crystal quality (similar to the bulk single crystalline Ge) and sufficiently reduced surface roughness. As a result, the Hall hole mobility of UTBB GeOI reaches 1330 cm2/V s with a carrier concentration of 2 × 1016 cm−3. The inversion mode UTBB GeOI nMOSFETs have also been demonstrated with suppressed mobility degradation during Ge layer thinning, indicating the feasibility of this GeOI substrate formation technique in future CMOS technologies.
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