- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Trap and 1/f-noise effects at the surface and core of GaN nanowire gate-all-around FET structure
摘要： Using capacitance, conductance and noise measurements, we investigate the trapping behavior at the surface and in the core of triangular-shaped one-dimensional (1D) array of GaN nanowire gate-all-around field effect transistor (GAA FET), fabricated via a top-down process. The surface traps in such a low dimensional device play a crucial role in determining the device performance. The estimated surface trap density rapidly decreases with increasing frequency, ranging from 6.07 × 1012 cm?2·eV?1 at 1 kHz to 1.90 × 1011 cm?2·eV?1 at 1 MHz, respectively. The noise results reveal that the power spectral density increases with gate voltage and clearly exhibits 1/f-noise signature in the accumulation region (Vgs > Vth = 3.4 V) for all frquencies. In the surface depletion region (1.5 V < Vgs < Vth), the device is governed by 1/f at lower frequencies and 1/f 2 noise at frequencies higher than ~ 5 kHz. The 1/f 2 noise characteristics is attributed to additional generation–recombination (G–R), mostly caused by the electron trapping/detrapping process through deep traps located in the surface depletion region of the nanowire. The cutoff frequency for the 1/f 2 noise characteristics further shifts to lower frequency of 102–103 Hz when the device operates in deep-subthreshold region (Vgs < 1.5 V). In this regime, the electron trapping/detrapping process through deep traps expands into the totally depleted nanowire core and the G–R noise prevails in the entire nanowire channel.
关键词： gate-all-around field effect transistor (FET),trap,nanowire,GaN,1/f-noise
更新于2025-09-23 15:22:29
-
Analysis of current transport mechanisms in sol-gel grown Si/ZnO heterojunction diodes in high temperature environment
摘要： This paper analyzes the electrical parameters of Si/ZnO heterojunction diodes in the wide temperature range, i.e. from room temperature (298 K) to 573 K to study the electrical performance of the diode in very high temperature environment. In this work, sol-gel derived nanostructured ZnO thin film was deposited directly on p-Si substrate using spin coating technique. Electrical parameters, such as rectification ratio, reverse saturation current, ideality factor, barrier height, series resistance and activation energy are derived from current-voltage characteristics of the device, measured using semiconductor parameter analyzer in the temperature range of 298 K–573 K for bias voltage of ± 5 V. The ideality factor, barrier height and series resistance is derived as 2.66, 0.789 eV and 3554 Ω respectively at 298 K, whereas at 573 K these are modified as 1.58, 1.15 eV and 801 Ω respectively. The above-mentioned results indicate the presence of spatial barrier height inhomogeneities (BHI) in high temperature environment. Hence, we have included the Gaussian distribution of spatial BHI in our analysis to calculate the effective Richardson constant (RC). Before inclusion of spatial BHI, RC was 4.026 × 10^{-6} Acm^{-2}K^{-2}. However, after inclusion of spatial BHI, RC is modified to 29.14 Acm^{-2}K^{-2}, which is nearer to the theoretical value (32 Acm^{-2}K^{-2}). Therefore, this study indicates that our as-fabricated Si/ZnO heterojunction diodes can sustain their electrical behaviour in very high temperature environment also and they are suitable for high temperature electronic and optoelectronic application.
关键词： Current-voltage characteristics,Richardson constant,Trap-assisted tunneling,Spatial barrier inhomogeneities,Heterojunction diode,Semiconductor thin film
更新于2025-09-23 15:22:29
-
Comparison between 403 nm and 497 nm repumping schemes for strontium magneto-optical traps
摘要： The theoretical description of the external degrees of freedom of atoms trapped inside a magneto-optical trap (MOT) often relies on the decoupling of the evolution of the internal and external degrees of freedom. That is possible thanks to much shorter timescales typically associated with the first ones. The electronic structure of alkaline-earth atoms, on the other hand, presents ultra-narrow transitions and metastable states that makes such an approximation invalid in the general case. In this article, we report on a model based on open Bloch equations for the evolution of the number of atoms in a magneto-optical trap. With this model we investigate the loading of the strontium blue magneto-optical trap under different repumping schemes, either directly from a Zeeman slower, or from an atomic reservoir made of atoms in a metastable state trapped in the magnetic quadrupolar field. The fluorescence observed on the strong 461 nm transition is recorded and quantitatively compared with the results from our simulations. The comparison between experimental results and calculations within our model allowed to identify the existence of the decay paths between the upper level of the repumping transition and the dark strontium metastable states, which could not be explained by electric dipole transition rates calculated in the literature. Moreover, our analysis pinpoints the role of the atomic movement in limiting the efficiency of the atomic repumping of the Sr metastable states.
关键词： cold atoms,magneto-optical trap,repumping schemes,inhomogeneous Bloch equations,alkaline-earth atoms
更新于2025-09-23 15:22:29
-
3D Magneto-Optical Trap of Yttrium Monoxide
摘要： We report three-dimensional trapping of an oxide molecule (YO), using a radio-frequency magneto-optical trap (MOT). The total number of molecules trapped is ～1.5 × 104, with a temperature of 4.1(5) mK. This diversifies the frontier of molecules that are laser coolable and paves the way for the second-stage narrow-line cooling in this molecule to the microkelvin regime. Futhermore, the new challenges of creating a 3D MOT of YO resolved here indicate that MOTs of more complex nonlinear molecules should be feasible as well.
关键词： laser cooling,molecular trapping,yttrium monoxide,3D magneto-optical trap
更新于2025-09-23 15:21:21
-
[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Effect of thermal pre-treatment on thermionic emission current stability from carbon nanotube forests
摘要： Carbon nanotube forests have great potential as efficient thermionic electron emitters due to a highly localized optical heating effect (“Heat Trap”). In past experiments, we observed a rapid decay in the emission current. In this work, we demonstrate that a relatively stable emission current can be achieved if the nanotube forest is pre-heated to 300 °C for 4 hours priors to electron emission. We attribute this improved current stability to the removal of reactant species, such as water trapped within the nanotube forest network.
关键词： Heat Trap,outgassing,lifetime,Carbon nanotubes,current stability,cathode,thermionic emission
更新于2025-09-23 15:21:21
-
Li Permeability Increase in Nano-Sized Amorphous Silicon Layers
摘要： Li permeation through nano-sized amorphous Si layers is investigated for temperatures up to 500°C (773 K) as a function of layer thickness between 12 and 95 nm. For the experiments the Si layers are embedded between 6Li and 7Li isotope enriched oxide based Li reservoirs and the thermally induced isotope exchange (through silicon layers and interfaces) is analyzed by Secondary Ion Mass Spectrometry in order to calculate Li permeabilities. The experiments reveal that the interface between silicon and the Li metal oxide does not hinder Li permeation and Li diffusion in silicon controls the overall process. The determined Li permeability increases drastically by orders of magnitude with decreasing silicon layer thickness, accompanied by a decrease in the activation enthalpy of Li permeation. These results can be explained by a gradual transition of trap-limited slow Li diffusion at high silicon thicknesses to interstitial fast Li diffusion at low Si thicknesses.
关键词： Li permeation,nano-sized layers,Li permeability,trap-limited diffusion,amorphous silicon,Secondary Ion Mass Spectrometry,isotope exchange,interstitial diffusion
更新于2025-09-23 15:21:21
-
Trap-Controlled White Electroluminescence From a Single Red-Emitting Thermally Activated Delayed Fluorescence Polymer
摘要： Single white-emitting polymers have been reported by incorporating the second-generation carbazole dendron into the side chain of a red-emitting thermally activated delayed ?uorescence (TADF) polymer. Due to the prevented hole trap effect, in this case, excitons can be generated simultaneously on the polymeric host and the red TADF dopant to give a dual emission. Consequently, a bright white electroluminescence is achieved even at a dopant loading as high as 5 mol.%, revealing a maximum luminous ef?ciency of 16.1 cd/A (12.0 lm/W, 8.2%) and Commission Internationale de l’Eclairage (CIE) coordinates of (0.42, 0.32). The results clearly indicate that the delicate tuning of charge trap is a promising strategy to develop ef?cient single white-emitting polymers, whose low-band-gap chromophore content can be up to a centesimal level.
关键词： carbazole dendron,thermally activated delayed ?uorescence (TADF),dual emission,charge trap,single white-emitting polymers
更新于2025-09-23 15:21:01
-
Revealing the compositional effect on the intrinsic long-term stability of perovskite solar cells
摘要： Understanding role of individual cation and halide components on the intrinsic long-term stability of perovskite solar cells (PSCs) is of great importance to pursue devices with high efficiency and superior long-term stability simultaneously. In this work, we report a low dopant content (1%) doping strategy to reveal the role of individual bromide and methylammoniun (MA) on the intrinsic operational stability of formamidinium lead iodide (FAPbI3-based) PSCs. This strategy enables us to tune the trap density of perovskite films while keep their apparent morphological and optical properties unchanged. Our results demonstrate that incorporation of MA into the FAPbI3-based PSCs is harmful to the long-term stability due to defect-induced degradation. And Br incorporation is beneficial to enhance the stability of FAPbI3-based PSCs via suppressing the trap density in the perovskite films. This work highlights the importance of defects management for improving the long-term operational stability of perovskite solar cells.
关键词： compositional effect,defects management,intrinsic stability,trap density,perovskite solar cells
更新于2025-09-23 15:21:01
-
Oriented Crystallization of Mixeda??Cation Tin Halides for Highly Efficient and Stable Leada??Free Perovskite Solar Cells
摘要： As the most promising lead-free branch, tin halide perovskites suffer from the severe oxidation from Sn2+ to Sn4+, which results in the unsatisfactory conversion efficiency far from what they deserve. In this work, by facile incorporation of methylammonium bromide in composition engineering, formamidinium and methylammonium mixed cations tin halide perovskite films with ultra-highly oriented crystallization are synthesized with the preferential facet of (001), and that oxidation is suppressed with obviously declined trap density. MA+ ions are responsible for that impressive orientation while Br- ions account for their bandgap modulation. Depending on high quality of the optimal MA0.25FA0.75SnI2.75Br0.25 perovskite films, their device conversion efficiency surges to 9.31% in contrast to 5.02% of the control formamidinium tin triiodide perovskite (FASnI3) device, along with almost eliminated hysteresis. That also results in the outstanding device stability, maintaining above 80% of the initial efficiency after 300 h of light soaking while the control FASnI3 device fails within 120 h. This paper definitely paves a facile and effective way to develop high-efficiency tin halide perovskites solar cells, optoelectronic devices, and beyond.
关键词： trap density,methylammonium bromide,oriented crystallization,tin halide perovskites,divalent tin ions
更新于2025-09-23 15:21:01
-
Shallow and Deep Trap States Passivation for Low-Temperature Processed Perovskite Solar Cells
摘要： While perovskite solar cells (PSCs) have emerged as promising low-cost solar power generators, most reported high-performance PSCs employ electron transport layers (ETLs, mainly TiO2) treated at high temperatures (≥450 °C), which may eventually hinder the development of flexible PSCs. Meanwhile, the development of low-temperature processed PSCs (L-PSCs) possessing performance levels comparable to that of high-temperature processed PSCs has actively been reported. In this study, L-PSCs with improved long-term stability and negligible hysteresis were developed through the effective passivation of shallow and deep traps in organic-inorganic hybrid perovskite (OIHP) crystals and at the ETL/OIHP interface. L-PSCs with alkaline chloride modification achieved state-of-the-art performance among reported L-PSCs (power conversion efficiency (PCE) = 22.6%) with a long-term shelf life. The origin of long-term stability and the efficient passivation of deep traps was revealed by monitoring the trap-state distribution. Moreover, the high PCE of a large-area device (21.3%, 1.12 cm2) were also demonstrated, confirming the uniformity of the modification.
关键词： trap states passivation,low-temperature processed,alkaline chloride modification,perovskite solar cells,long-term stability
更新于2025-09-23 15:21:01