All-inorganic perovskite quantum dots (QDs) have widely used in a lot of micro-nano photoelectric devices. However, resistive random access memory (RRAM) devices based on All-inorganic perovskite QDs are relatively scarce. In this work, a RRAM, which exhibits the write-once-read-many-times (WORM) memory effect, based on CsPbBr3 QDs was successfully fabricated by solution processed method at room temperature. The CsPbBr3 QDs based memory shows great reproducibility, good data retention ability, irreversible electrical transition from the high resistance state (HRS) or OFF state to the low resistance state (LRS) or ON state and the resistance ratio (ON/OFF) can reach almost 107. To study the CsPbBr3 QDs based WORM memory provides an opportunity to develop the next generation high-performance and stable WORM devices.
We fabricate and investigate the photoelectrical characterization of PbSe QDs FEpTs Field Effect photo Transistors in lateral (LQFEpT) and vertical architectures (VQFEpT) respectively. Both LQFEpT and VQFEpT apply PbSe quantum dots as active layer, with different channel length of 0.1mm and 678nm respectively. The VQFEpT apply Au/Ag nanowires (NWs) as source transparent electrode connecting with Au source electrode. The ambipolar operation of both FEpTs show low power consumption, delivering high drain current at VSD = VG = ± 4 V. The VQFEpT exhibit higher photocurrent up to 4mA, three orders magnitude higher than that in LQFEpTs (16μA), owing to the superior carrier transportion in the shorter channel. As a result, higher photo responsivity (8×104A/W), specific detectivity (2×1012Jones) and gain (1.3× 105) are achieved in VQFEpT. The all-solution processing vertical architecture provide a convenient way for IR photo detectors with high performances.
Stable and homogeneous dye-doped cholesteric liquid crystals (DDCLCs) were prepared. The lasers generated from DDCLCs can be tuned by temperature, and the working temperature range of DDCLCs was from 20 °C to 60 °C. After adding bi-functional monomer RM257 and photoinitiator Irgacure 2959, the working temperature range of lasers from DDCLCs was enhanced from 20-60 °C to 20-70 °C.
In this paper, a hybrid CMOS inverter employing In-Ga-Zn oxide (IGZO) (inorganic, n-channel) and P3HT (organic, p-channel) thin film transistors (TFTs) is reported. Both inorganic and organic TFTs are fabricated by ink-jet printing technology. The field effect mobility of p and n channel TFTs are 0.0038 and 0.27 cm2/V s, respectively. The inverter exhibited an obvious inverter response for switching between logic ‘1’ and logic ‘0’, and yielded a high gain of 14 at VDD = 30 V. With the combining advantages of oxide semiconductor (n-type, high mobility) and organic (commonly p-type), it is promising to construct powerful functional CMOS circuits, such as ring oscillator and shift registers.
The influence of the metallic electrode materials on the contact resistance of the ink-jet printed In-Ga-Zn oxide (IGZO) thin film transistors (TFTs) is investigated in this paper. Various electrodes, including Al, Ti/Au, ITO and Au were examined based on the inverted staggered (bottom gate top contact) IGZO TFTs. Without additional annealing, the contact resistance increased with the increase of the work function of the electrode, which is Al < Ti/Au < ITO < Au. However, the contact resistance behavior changed drastically for different electrodes under different annealing temperature from 200 to 500 °C. The different behavior of the electrodes upon annealing was regarded to the contact modes changed between ohmic and Schottky contact. The finding provides a clue for electrode selection for the ink-jet printed IGZO TFTs to minimize the contact resistance and optimize the device performance according to the process conditions.
InGaN/GaN blue light emitting diodes with varied quantum well thickness from 2.4 nm to 3.6 nm are fabricated and
characterized by atmosphere pressure metalorganic chemical vapor deposition (AP-MOCVD). Experimental results
show that the exciton localization effect is enhanced from 21.76 to 23.48 by increasing the quantum well thickness
from 2.4 nm to 2.7 nm. However, with the further increase of quantum well thickness, the exciton localization effect
becomes weaker. Meanwhile, the peak wavelength of electroluminescence redshift with the increase of well
thickness due to the larger quantum confined Stark effect (QCSE). In addition, the efficiency droop can be improved
by increasing the well thickness.
ZnO and Ag-doped ZnO nanorods are fabricated by hydrothermal method. Effects of Ag doping on the ZnO nanorods have been investigated by various measurements. Introduction of Ag in ZnO nanorods has no effects on the surface morphology and growth habits of ZnO. Compared to ZnO nanorods, absorption wavelength shifts red after Ag doping, corresponding to decrease of optical band gap. It is suggested that defects band is introduced into Ag-doped ZnO. Luminescence of Ag-doped ZnO nanorods have been found to have two emission peaks centering at around 520 nm and 680 nm, which can be explained by oxygen vacancy and introduced defects, respectively. ZnO and Ag-doped ZnO nanorods inorganic/organic heterostructure LEDs are reported. The junction consists of nanorods and polymer, which is evaporated or spin-coated on the samples. Ag doping ZnO nanorods inorganic/organic heterostructure LED shows smaller leakage current and better rectification characteristic than pure ZnO nanorods LED device.
Quantum dot light-emitting diodes (QD-LEDs) have recently attracted much attention due to its highly saturated
emission color and the capability of tuning the emission color by means of engineering its size. In this letter, an allinorganic
light-emitting diode based on colloidal core/shell CdS/ZnS nanocrystal quantum dots (QDs) emissive layer
sandwiched between p-type NiO and n-type ZnO is reported. NiO and ZnO layers are deposited by means of the lowcost
spin coating technique. The device showed a rectification behavior and QD light emission with the
electroluminescent emissions at 605nm.
As a fine material widely used in solar cells, electrochromic devices and an excellent photocatalyst, Titanium dioxide
(TiO2) has attracted more and more attention. There are many factors that affect the properties of TiO2 thin films
including reaction temperature, reaction time and concentration. The influence of the pH of the precursor solution on the
formation of TiO2 thin films, however, has not been studied thoroughly. Involved in the solution such as Hydrochloric
acid (HCl) or urea ((NH2)2CO) reagent, the pH of the solution can be controlled by the ratio of both. During the
experiment, which involves the hydrolysis reaction of Ti3+, changing the pH of the solution will affect the speed of the
reaction rate and film thickness. Therefore, the pH of the solution affects the surface morphology of the TiO2 thin films.
The growth of TiO2 with different pH shows unequable states. Through the observation and characterization of the
experimental results, we can optimize the pH of the growth environment.
In this paper, we present one planar graded photonic quasicrystals based on phyllotaxy structure (PSPQ) to mimic the Luneburg lens. The PSPQ is composed by discrete cylinders, which radius are determined by the index profile of Luneburg lens and Maxwell-Garnett effective medium theory, to mimic the graded index (GRIN) materials. Numerical simulations are performed to investigate the focusing features of the PSPQs by means of finite difference time domain (FDTD) methods. Numerical results show that the PSPQs-based Luneburg lens can focus the light more tightly and efficiently in comparison with conventional graded photonic crystals. Meanwhile, we also explored the focusing properties of PSPQs with different generating angle, which determined the spiral type of phyllotaxy structures, to optimize the focusing behavior of the proposed devices.
The concept of fractal, such as Cantor set, has been combined with the Fresnel zone plates (ZPs) to improve its imaging
capability and introduce additional freedom for optimizing. In this letter, Fibonacci zone plates (FiZPs), which is
generated by means of Fibonacci fractals, was proposed. The FiZPs can be constructed by the generating rules of the
Fibonacci sequences similar with the Cantor set zone plate published. Numerical simulation based on Fresnel diffraction
is performed to verify the on-axis intensity distribution of the FiZPs. According to the simulated results, the FiZPs can
focus the incident beam as conventional zone plates as well but with fractal on-axis intensity profile. The theoretical
results are also verified by the experiment by means of phase-only spatial light modulator (pSLM).
Furthermore, the spiral Fibonacci zone plate (sFiZPs) was designed by overlapping the spiral phase on the FiZPs. Both
numerical simulations and experiments are performed and the results are coincident well with each other.
A new kind of bowtie related structures, Sierpinski complementary bowtie aperture (SCBA), is proposed for enhancing
and confining optical magnetic field. The magnetic field enhancement factor can be improved with the presence of the
fractal. Numerical simulation shows that higher iteration of the SCBA is responsible for the variation of the resonant
wavelengths. The magnetic field distributions illustrated 10nm above the output plane prove the magnetic intensity is
confined in the sub-wavelength scale. Further investigation demonstrates current can be enhanced in the center of the
apertures while electric fields are found to be easier to concentrate at the tiny fractal structures. Magnetic intensity
distributions at several resonant points in the spectrum of the third-iteration SCBA are also plotted and the longer
wavelength region in near infrared is found to be unsuited for confining magnetic field in SCBA due to weak interaction
with the fractals.
Traditionally LC/polymer composite, such as polymer dispersed liquid crystal (PDLC), holographic PDLC
(H-PDLC), and polymer stabilized liquid crystal (PSLC) etc. is primarily used as display devices. Recently, with
electrical, optical and thermal tunability, easy fabrication and fast response time, they have attracted much attention
in photonics devices (grating, diffractive optical elements, optical switches etc.) with potential applications in
communications, imaging, and biology. The intrinsic tunable property of LC/polymer composite (by means of
mechanic, electronic, magnetic, thermal stimulus) makes it an attractive material used in dynamic photonics
devices. In this paper, we will first introduce the preparation of LC/polymer material for various objectives. Then
two essential fabrication approaches i.e. multibeams interference lithography for periodic structures and
programmable projection lithography for specific designed patterns are introduced respectively. At last, our recent
results in applying LC/polymer composite in photonic devices, such as tunable 3D photonics crystals, 2D tunable
lasing source, focusing elements and binary Airy beams generation etc. are reviewed.
Several modes are simulated in parameter space to find profitable mode for amp SLM design and RTN52° with high reflectance, high dDn and low phase shift is used for experiment. The reflectance and contrast are measured on a RTN52° LCOS device.
Optimize the working model of LCoS (Liquid Crystal on Silicon) in parameter space by simulation. Two models are selected, which is suitable for phase modulating. One is the RTN-52° model, the other is parallel alignment ECB model. Phase changing is measured when various voltage are applied to Lcos. Show some results when the Lcos is used as a Fresnel lens.
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