Recent progress of interface self-assembled monolayers engineering organic optoelectronic devices

Numerous reports have suggested that the performance of organic optoelectronic devices based on organicfieldeffect transistors(OFETs)is largely dependent on their interfaces.Self-assembled monolayers(SAMs)have been commonly used to engineer the interfaces of high-performance devices,particularly due to their well-defined structures and simple operation process through simple chemical adsorption growth.In this review,the structures of OFETs and SAM-modified OFETs are described,while different SAMs have been characterized.Furthermore,recent advances in the interface engineering of OFETs are described,the applicability of SAMs in functional devices of OFETs is reviewed,and existing problems and future developments in thisfield have been identified.

Controller Design for a 3 D.O.F Haptic Interface Device

This paper presents a 3 D.O.F haptic interface which is designed to meet the interaction requirement of teleoperation tasks and virtual reality applications. The mechanism design takes the operability into consideration such as adopting steel cable as transmission component and mass balance to eliminate the gravity effect. The dynamics of haptic interface including actuating device is studied. In order to provide operator with fidelity kinesthetic information, a force controller using self-learning fuzzy logic control is designed. The simulation results verify the effectiveness of the control method.

Effect of Switching on Metal-Organic Interface Adhesion Relevant to Organic Electronic Devices

Considerable efforts are currently being devoted to investigation of metal-organic, organic-organic and organic-inorganic interfaces relevant to organic electronic devices such as organic light emitting diode (OLEDs), organic photovoltaic solar cells, organic field effect transistors (OFETs), organic spintronic devices and organic-based Write Once Read Many times (WORM) memory devices on both rigid and flexible substrates in laboratories around the world. The multilayer structure of these devices makes interfaces between dissimilar materials in contact and plays a prominent role in charge transport and injection efficiency which inevitably affect device performance. This paper presents results of an initial study on how switching between voltage thresholds and chemical surface treatment affects adhesion properties of a metal-organic (Au-PEDOT:PSS) contact interface in a WORM device. Contact and Tapping-mode Atomic Force Microscopy (AFM) gave surface topography, phase imaging and interface adhesion properties in addition to SEM/EDX imaging which showed that surface treatment, switching and surface roughness all appeared to be key factors in increasing interface adhesion with implications for increased device performance.

Alcohol-dispersed polymer complex as an effective and durable interface modifier for n-i-p perovskite solar cells

Abundant interfacial defects remain a significant challenge that hampers both the efficiency and stability of perovskite solar cells(PSCs).Herein,an alcohol-dispersed conducting polymer complex,denoted as PEDOT:F(Poly(3,4-ethylene dioxythiophene):Perfluorinated sulfonic acid ionomers),is introduced into the interface between perovskite and hole transporting layer in regular-structured PSCs.PEDOT:F serves as a multi-functional interface layer(filling grain boundaries and covering perovskite's grain-surface)to achieve a robust interaction with organic groups within perovskites,which could induce a structural transformation of PEDOT to increase its conductivity for the efficient hole-transport.Furthermore,the strong interaction between PEDOT and perovskites could promote an effective coupling of undercoordinated Pb~(2+)ions with the lone electron pairs near O&S atoms in PEDOT molecules,thereby enhancing defect passivation.Additionally,PEDOT:F with inherent hydrophobic properties prevents effectively moisture invasion into perovskites for the improved long-term stability of the PSCs.Consequently,the PEDOT:F-based PSCs achieved a champion efficiency of 24.81%,and maintained ca.92%of their initial efficiency after 7680 h of storage in a dry air environment,accompanied by the enhanced photothermal stability.

Investigation of interface materials for enhancing stability in nonfullerene solar cells

Organic solar cells(OSCs)have attracted attention due to their lightweight nature,flexibility,and facile preparation using solution-based methods.Their efficiency has been further elevated by the rapid advancement of nonfullerene materials,achieving individual cell efficiencies that surpass 19%.Hence,the stability of nonfullerene solar cell production must be scrutinized.The stability of the cathode interface layer significantly impacts the overall stability of OSC devices.PFN-Br,a commonly employed cathode interface material,is susceptible to degradation due to its sensitivity to environmental humidity,consequently compromising the device stability.In this study,we introduce fluorescent dye molecules,rhodamine 101,as cathode interface layers in OSCs to establish device stability and assess their universality.A comparative investigation of rhodamine 101 and PFN-Br devices demonstrates the former’s distinct advantages in terms of thermal stability,photostability,and storage stability even without encapsulation,particularly in an inert environment.By employing the Kelvin probe,we compare the work function of different cathode interface films and reveal that the work function of the rhodamine 101 interface material remains relatively unaffected by environmental factors.As a consequence,the device performance stability is significantly enhanced.The application of such fluorescent dye molecules extends the scope of cathode interface layers,amplifies device stability,and propels industrialization.

New Forward Gated-Diode Technique for Separating Front Gate Interface- from Oxide-Traps Induced by Hot-Carrier-Stress in SOI-NMOSFETs

The front gate interface and oxide traps induced by hot carrier stress in SOI NMOSFETs are studied.Based on a new forward gated diode technique,the R G current originating from the front interface traps is measured,and then the densities of the interface and oxide traps are separated independently.The experimental results show that the hot carrier stress of front channel not only results in the strong generation of the front interface traps,but also in the significant oxide traps.These two kinds of traps have similar characteristic in increasing with the hot carrier stress time.This analysis allows one to obtain a clear physical picture of the effects of the hot carrier stress on the generating of interface and oxide traps,which help to understand the degradation and reliability of the SOI MOSFETs.

A Method to Separate Effects of Oxide-Trapped Charge and Interface-Trapped Charge on Threshold Voltage in pMOSFETs Under Hot-Carrier Stress

A simple new method based on the measurement of charge pumping technique is proposed to separate and quantify experimentally the effects of oxide-trapped charges and interface-trapped charges on threshold voltage degradation in p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) under hot-carrier stress.Further,the experimental results verify the validness of this method.It is shown that,all three mechanisms of electron trapping effect,hole trapping effect and interface trap generation play important roles in p-channel MOSFETs degradation.It is noted that interface-trapped charge is still the dominant mechanism for hot-carrier-induced degradation in p-channel MOSFETs,while a significant contribution of oxide-trapped charge to threshold voltage is demonstrated and quantified.

Thermal Spray Coating of Tungsten for Tokamak Device

Thermal spray, such as direct current （d.c.） plasma spray or radio frequency induced plasma spray, was used to deposit tungsten coatings on the copper electrodes of a tokamak device. The tungsten coating on the outer surface of one copper electrode was formed directly through d.c. plasma spraying of fine tungsten powder. The tungsten coating/lining on the inner surface of another copper electrode could be formed indirectly through induced plasma spraying of coarse tungsten powder. Scanning electron microscopy （SEM） was used to examine the cross section and the interface of the tungsten coating. Energy Dispersive Analysis of X-ray （EDAX） was used to analyze the metallic elements attached to a separated interface. The influence of the particle size of the tungsten powder on the density, cracking behavior and adhesion of the coating is discussed. It is found that the coarse tungsten powder with the particle size of 45-75μm can be melted and the coating can be formed only by using induced plasma. The coating deposited from the coarse powder has much higher cohesive strength, adhesive strength and crack resistance than the coating made from the fine powder with a particle size of 5μm.

Photoluminescence of a ZnO/GaN Heterostructure Interface

Growth of a ZnO/GaN heterostructure is carried out using pulsed laser deposition. By etching the ZnO layer from the ZnO/GaN structure, the photoluminescence （PL） of the associated GaN layer shows that the donor- acceptor luminescence of CaN shifts to about 3.27eV, which is consistent with the electroluminescence （EL） of n-ZnO/p-GaN already reported. XPS shows that oxygen diffuses into the CaN crystal lattice from the surface to 20nm depth. The PL spectra at different temperatures and excitation densities show that oxygen plays the role of potential fluctuation. The associated PL results of the interface in these LEDs could be helpful to understand the mechanism of EL spectra for ZnO/CaN p-n junctions.

Total ionizing dose effect of gamma rays on H-gate PDSOI MOS devices at different dose rates

The total dose effect of ^(60)Co γ-rays on 0.8μm H-gate partially depleted-silicon-on-insulator NMOS devices was investigated at different irradiation doses. The results show that the shift in saturation current at high dose rate is greater than that at low dose rate, due to increase in interface-state density with decreasing dose rate; the scattering effect of interface state on electrons in the channel causes degradation in carrier mobility; and the body current and transconductance of the back gate enhance low-doserate sensitivity when the irradiation is under OFF-bias. A double transconductance peak is observed at 3 kGy(Si)under high dose rates.

Effect of NO annealing on charge traps in oxide insulator and transition layer for 4H-SiC metal–oxide–semiconductor devices

The effect of nitric oxide（NO） annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor（MOS） devices has been investigated using the time-dependent bias stress（TDBS）,capacitance–voltage（C–V）,and secondary ion mass spectroscopy（SIMS）.It is revealed that two main categories of charge traps,near interface oxide traps（Nniot） and oxide traps（Not）,have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.

A New Conducting Polymer Electrode for Organic Electroluminescence Devices

Conducting polymer polydimethylsiloxane （PDMS） is studied for the high performance electrode of organic electroluminescence devices. A method to prepare the electrode consisting of a SiC thin film and PDMS is investigated. By using ultra thin SiC films with different thicknesses, the organic electroluminescence devices are obtained in an ultra vacuum system with the model device PDMS/SiC/PPV/Alq3, where PPV is poly para-phenylene vinylene and Alq3 is tris（S-hydroxyquinoline） aluminium. The capacitance voltage （C - V）, capacitance-frequency （C - F）, current-voltage （I - V）, radiation intensity-voltage （R - V） and luminance eFficiency-voltage （E - V） measurements are systematically studied to investigate the conductivity, Fermi alignment and devices properties in organic semiconductors. Scanning Kelvin probe measurement shows that the work function of PDMS/SiC anode with a 2.5-nm SiC over layer can be increased by as much as 0.28eV, compared to the conventional ITO anode. The result is attributed to the charge transfer effect and ohmic contacts at the interface.

In-situ characterization of electrochromism based on ITO/PEDOT:PSS towards preparation of high performance device

Poly（3,4-ethylenedioxythiophene）：poly（styrenesulfonate）（PEDOT：PSS） is usually sandwiched between indium tin oxide（ITO） and a functional polymer in order to improve the performance of the device. However, because of the strong acidic nature of PEDOT：PSS, the instability of the ITO/PEDOT：PSS interface is also observed. The mechanism of degradation of the device remains is unclear and needs to be further studied. In this article, we investigate the in-situ electrochromism of PEDOT：PSS to disclose the cause of the degradation. X-ray photoelectron spectroscopy（XPS） was used to characterize the PEDOT：PSS films, as well as the PEDOT：PSS plus polyethylene glycol（PEG） films with and without indium ions. The electrochromic devices（ECD） based on PEDOT：PSS and PEG with and without indium ions are carried out by in-situ micro-Raman and laser reflective measurement（LRM）. For comparison, ECD based on PEDOT：PSS and PEG films with LiCl, KCl, NaCl or InCl_3 are also investigated by LRM. The results show that PEDOT：PSS is further reduced when negatively biased, and oxidized when positively biased. This could identify that PEDOT：PSS with indium ions from PEDOT：PSS etching ITO will lose dopants when negatively biased. The LRM shows that the device with indium ions has a stronger effect on the reduction property of PEDOT：PSS-PEG film than the device without indium ions. The contrast of the former device is 44%, that of the latter device is about 3%. The LRM also shows that the contrasts of the device based on PEDOT：PSS＋PEG with LiCl, KCl, NaCl, InCl_3 are 30%, 27%, 15%, and 18%, respectively.

A review of ultrafast laser micro/nano fabrication:Material processing,surface/interface controlling,and devices fabrication

Ultrafast laser processing technology has offered a wide range of opportunities in micro/nano fabrication and other fields such as nanotechnology,biotechnology,energy science,and photonics due to its controllable processing precision,diverse processing capabilities,and broad material adaptability.The processing abilities and applications of the ultrafast laser still need more exploration.In the field of material processing,controlling the atomic scale structure in nanomaterials is challenging.Complex effects exist in ultrafast laser surface/interface processing,making it difficult to modulate the nanostructure and properties of the surface/interface as required.In the ultrafast laser fabrication of micro functional devices,the processing ability needs to be improved.Here,we review the research progress of ultrafast laser micro/nano fabrication in the areas of material processing,surface/interface controlling,and micro functional devices fabrication.Several useful ultrafast laser processing methods and applications in these areas are introduced.With various processing effects and abilities,the ultrafast laser processing technology has demonstrated application values in multiple fields from science to industry.

Weak Gate Effect in 1,3-Benzenedithiol Molecular Device

We introduce a full interaction Hamiltonian method to the generalized quantum chemical approach and apply it to investigate the electron tunneling properties of 1,3-benzenedithiol molecular device. The weak gate effect we calculate is consistent with the experiment. The asymmetric current character mainly comes from the asymmetry of the molecule and the nonlinear responding to the gate electric field.

Effect of Interface Nanotexture on Light Extraction of InGaN-Based Green Light Emitting Diodes

We report the enhancement of the light extraction of InGaN-based green light emitting diodes （LEDs） via the interface nanotexturing. The texture consists of high-density nanocraters on the surface of a sapphire substrate with an in situ etching. The width of nanocraters is about 0.5 μm and the depth is around 0.1 μm. It is demonstrated that the LEDs with interface texture exhibit about a 27% improvement in luminance intensity, compared with standard LEDs. High power InGaN-based green LEDs are obtained by using the interface nanotexture. An optical ray-tracing simulation is performed to investigate the effect of interface nanotexture on light extraction.

Influences of Interface States on Resistive Switching Properties of TiOx with Different Electrodes

Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal？insulator-metal （MIM） structures for studying the properties and mechanisms of resistive switching. The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states, which are displayed as ohmic-like or non-ohmic contact. Based on the interface states, the electrical models for MIM devices are analyzed and extracted. The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions. All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.

Development of Jet Training FTD (Flight Training Device) Overhead System

Today, the growth of aerospace industry has led to the development of modular overhead systems that can be applied to a wide variety of aircraft.?It actually maximizes training effectiveness by working in a similar way as to the real aircraft maneuverability. Overhead system control device for aircraft simulator is developed as a module and integrated to the flight simulator. The developed system can replace the similar products imported from overseas at a much lower price, about one third of the imports, while maintaining the same level of functionality and the performance with the counterparts. This price advantage is the main motivation of this development, which is expected to enlarge the commercial training simulator market in our country. This development has been also funded by the government, and we invited several commercial airline pilots to test the equipment. The post operation interview revealed that the developed system at least matches or exceeds the performance of the imported products. With the development completed, it is ready for the commercial production and will help promote the expansion of flight training education at various aerospace universities in Korea.

Exploring how hydrogen at gold-sulfur interface affects spin transport in single-molecule junction

Very recently,experimental evidence showed that the hydrogen is retained in dithiol-terminated single-molecule junction under the widely adopted preparation conditions,which is in contrast to the accepted view[Nat.Chem.11351(2019)].However,the hydrogen is generally assumed to be lost in the previous physical models of single-molecule junctions.Whether the retention of the hydrogen at the gold-sulfur interface exerts a significant effect on the theoretical prediction of spin transport properties is an open question.Therefore,here in this paper we carry out a comparative study of spin transport in M-tetraphenylporphyrin-based(M=V,Cr,Mn,Fe,and Co;M-TPP)single-molecule junction through Au-SR and Au-S(H)R bondings.The results show that the hydrogen at the gold-sulfur interface may dramatically affect the spin-filtering efficiency of M-TPP-based single-molecule junction,depending on the type of transition metal ions embedded into porphyrin ring.Moreover,we find that for the Co-TPP-based molecular junction,the hydrogen at the gold-sulfur interface has no obvious effect on transmission at the Fermi level,but it has a significant effect on the spin-dependent transmission dip induced by the quantum interference on the occupied side.Thus the fate of hydrogen should be concerned in the physical model according to the actual preparation condition,which is important for our fundamental understanding of spin transport in the single-molecule junctions.Our work also provides guidance in how to experimentally identify the nature of gold-sulfur interface in the single-molecule junction with spin-polarized transport.