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High infrared transmittance CdS single crystal grown by physical vapor transport
摘要： Φ55 × 15 mm2 CdS bulk single crystal with high infrared transmittance was grown by physical vapor transport. The single crystal has a consistent structure from top to bottom, which was confirmed by X-ray diffraction. The (002) full-width at half-maximum of the X-ray diffraction was measured to be 60.00 arcsec, indicating a good quality of the structure. Hall mobility, specific resistivity, and carrier concentration for the top and bottom of the crystal were observed as well. Transmittance for the CdS single crystal was measured to be higher than 70% from 2.5 to 4.5 μm, making the single crystal an important candidate for infrared window materials. Furthermore, the absorption mechanism of the CdS single crystal was analyzed.
关键词： physical vapor transport,X-ray diffraction,semiconducting materials,single crystal growth
更新于2025-09-23 15:23:52
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Buried defects induced by plasma assisted molecular beam epitaxy of AlN and GaN on Silicon
摘要： The present work is dedicated to the study of peculiar defects observed in GaN/AlN structures grown on Silicon substrate using the plasma assisted Molecular Beam Epitaxy under metal-rich conditions. Optical microscopy shows that these defects have unde?ned shape when AlN is grown on Silicon. On the contrary such defects are not observed with AlN ?lms grown under nitrogen-rich plasma assisted or ammonia source Molecular Beam Epitaxy, but triangular shape defects appear in case of GaN regrowth on the latter. As scanning electron microscopy is not able to evidence these defects but only protuberances connected with them, we deduce that they are located in the Silicon substrate. Complementary analysis with atomic force microscopy and energy dispersive X-ray analysis lead us to propose a scenario involving the etching of the Silicon substrate with Ga or Al di?using through weak points in the nucleation layer.
关键词： A1. Defects,B1. Nitrides on Silicon,A3. Molecular beam epitaxy,B2. Semiconducting materials
更新于2025-09-23 15:21:21
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Controlled growth of MoS2 by atomic layer deposition on patterned gold pads
摘要： Approaches to synthesize large-area MoS2 thin films have been extensively investigated in recent years towards system-level micro-/nanoelectronics applications. Methods including chemical vapor deposition (CVD) and atomic layer deposition (ALD) can enable uniform and wafer-scale MoS2 films on insulating substrates, but without selective control on the growth location. Herein, we report a controlled growth of ultra-thin MoS2 films on Au pads patterned on insulating substrates by using ALD-based techniques. Clear difference in the incubation period duration of the ALD process among different substrate surfaces have been observed. Selective growth of MoS2 can be achieved on patterned Au on SiO2/Si substrate while the incubation period is shorter on sapphire substrate as compared with that on SiO2/Si. In addition, the influence of deposition temperature on the film growth dynamics on difference surfaces has been studied. Such controlled growth of MoS2 by ALD can be very attractive in future optoelectronics applications and the synthesis on patterned Au is promising in fulfilling its application potentials such as electrocatalyst in hydrogen evolution reaction.
关键词： B2. Semiconducting materials,A3. Atomic layer deposition,B1. Sulfides
更新于2025-09-23 15:19:57
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Spectroscopic Studies of Charge-Transfer Character and Photoresponses of F <sub/>4</sub> TCNQ-Based Donora??Acceptor Complexes
摘要： F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) is used widely as a hole-doping agent in photoresponsive organic semiconducting materials, yet relatively little is known about the photoresponses of the F4TCNQ?? anion generated via doping. Furthermore, there is still relatively little systematic exploration of how the properties of the local material or chemical environment impacts the driving force for generating these charge-transfer complexes. Here we present spectroscopic and photophysical studies of F4TCNQ in charge-transfer complexes (CTCs) with the electron donor N,N′-diphenyl-N-N′-di-p-tolylbenzene-1,4-diamine (MPDA) both in dichloroethane solution and polystyrene matrices. Integer charge transfer (ICT) between donor and acceptor occurs readily in dichloroethane solvent to form F4TCNQ??:MPDA+ CTCs, due to a ～150 mV difference in MPDA+/MPDA and F4TCNQ/F4TCNQ?? reduction potentials. Ultrafast spectroscopic studies of the CTC as well as electrochemically generated F4TCNQ?? and MDPA+ reveal that the photoresponses of these CTCs are dominated by that of the dopant anion, including rapid deactivation (800 fs) after excitation to the anion D1 excited state, followed by slower (～10 ps) vibrational cooling in the anion D0 state. Excitation to the higher-lying D2 state results in a rapid relaxation to the D1 state, in contrast to direct D2 → D0 relaxation previously observed for F4TCNQ?? in the gas phase. CTCs embedded in polystyrene (PS) matrices are observed to lose their integer charge-transfer character upon evaporation of solvent, as evidenced by changes to electronic and vibrational absorption features associated with F4TCNQ??. This change is attributed to the loss of solvent stabilization of the ion pair formed through the charge-transfer reaction. Ultrafast spectral measurements reveal that the photoresponses of the partial charge-transfer (PCT) species embedded in PS are still highly similar to those of the ICT species and unlike that of neutral F4TCNQ, implying the electronic properties of the PCT state are likewise dominated by properties of the reduced acceptor molecule. We conclude that excitation of ICT or PCT states introduces optical losses for photoresponses of doped organic semiconductor materials due to the large anion absorption cross section and its rapid, dissipative deactivation dynamics.
关键词： photoresponses,ultrafast spectroscopy,charge-transfer complexes,F4TCNQ,organic semiconducting materials
更新于2025-09-23 15:19:57
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A novel electrochemical method for simultaneous measurement of real-time potentials and photocurrent of various photoelectrochemical systems
摘要： Two-electrode configuration is preferably used in practical application of various photoelectrochemical systems, such as green fuel production and cathodic protection. Photo electrodes are extendedly studied but the effects of the dark electrodes on overall performance of PEC systems are not experimentally figured out. To address this issue, herein, a novel electrochemical method achieving simultaneous measurement of photocurrent and real-time potential of the photo electrode and the dark electrode is proposed. With this method, the actual band positions and band bending of the photo electrode under photocurrent going through can be determined correctly. By investigating photoelectrochemical hydrogen production and cathodic protection with ZnO photo anodes, it is revealed that the amplitude of photocurrent is not solely determined by the number of light generated electrons on the photo electrode but also strongly affected by their consuming rate for electrochemical reactions on the dark electrode. These applications demonstrate the practicality, reliability and universality of the proposed method for comprehensive understanding the reactions of various photoelectrochemical systems and eventually for their better development.
关键词： Semiconducting materials,Artificial solar synthesis,Photoelectrochemical cathodic protection,Photocatalysis,Photoelectrochemical water splitting
更新于2025-09-19 17:15:36
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Facile Synthesis and Visible Light Photocatalytic Activity of Sn <sub/> 1- <i>x</i> </sub> Mn <sub/><i>x</i> </sub> S (0 ≤ <i>x</i> ≤ 0.20) Nanocrystals
摘要： Tin-sulfide (SnS) has emerged as a promising energy-material owing to its remarkable optical and electrical properties. SnS can exhibit even more diversified properties with the incorporation of other elements, but remains scantly explored. The optical and photocatalytic properties of Mn-substituted SnS (Sn1-xMnxS with 0 ≤ x ≤ 0.2) nanocrystals are reported here. Mn-incorporation into SnS is inferred from structural and photoelectron spectroscopic study. Transmission electron microscopy reveals a change in the size-cum-morphology of nanocrystals with Mn- substitution. While cuboid shape nanocrystals are observed for SnS, Mn-substitution results in spherical shape. The optical band gap of Sn1-xMnxS shows a red-shift (by 0.15 eV) up to 10% Mn-concentration, however further substitution leads to contrasting effect. The intensity of emission peaks declines significantly upon Mn-substitution, which could be related to charge-separation scenario that weakens the radiative recombination process. Mn- substitution in SnS enhances the photocatalytic activity on the degradation of Congo red dye in visible region. The scavenger study suggests that the photo generated hole, hydroxyl and super oxide radicals are the principal reacting species for the degradation of Congo red dye. The tunability of optical properties in Sn1-xMnxS and enhanced photocatalytic properties could make it suitable for potential applications in photocatalysis and photovoltaics.
关键词： Chalcogenides,Semiconducting materials,Nano Crystals,Photocatalysis
更新于2025-09-10 09:29:36