Surface charge transfer doping of graphene using a strong molecular dopant CN6-CP

Surface charge transfer doping of graphene plays an important role in graphene-based electronics due to its simplicity,high doping efficiency,and easy-controllability.Here,we demonstrate the effective surface charge transfer hole doping of graphene by using a strong p-type molecular dopant hexacyanotrimethylene-cyclopropane (CN6-CP).The CN6-CP exhibits a very high intrinsic work function of 6.37 e V,which facilitates remarkable electron transfer from graphene to CN6-CP as revealed by in situ photoelectron spectroscopy investigations.Consequently,hole accumulation appears in the graphene layer at the direct contact with CN6-CP.As evidenced by Hall effect measurements,the areal hole density of graphene significantly increased from 8.3×10^(12)cm^(-2) to 2.21×10^(13)cm^(-2) upon 6 nm CN6-CP evaporation.The CN6-CP acceptor with strong p-doping effect has great implications for both graphene-based and organic electronics.

Modulating magnetism of nitrogen-doped zigzag graphene nanoribbons

We present a study of electronic properties of zigzag graphene nanoribbons （ZGNRs） substitutionally doped with nitrogen atoms at a single edge by first principle calculations. We find that the two edge states near the Fermi level sepa- rate due to the asymmetric nitrogen-doping. The ground states of these systems become ferromagnetic because the local magnetic moments along the undoped edges remain and those along the doped edges are suppressed. By controlling the charge-doping level, the magnetic moments of the whole ribbons are modulated. Proper charge doping leads to interest- ing half-metallic and single-edge conducting ribbons which would be helpful for designing graphene-nanoribbon-based spintronic devices in the future.

Surface charge transfer doping for two-dimensional semiconductor-based electronic and optoelectronic devices

Doping of semiconductors,i.e.,accurately modulating the charge carrier type and concentration in a controllable manner,is a key technology foundation for modern electronics and optoelectronics.However,the conventional doping technologies widely utilized in silicon industry,such as ion implantation and thermal diffusion,always fail when applied to two-dimensional(2D)materials with atomically-thin nature.Surface charge transfer doping(SCTD)is emerging as an effective and non-destructive doping technique to provide reliable doping capability for 2D materials,in particular 2D semiconductors.Herein,we summarize the recent advances and developments on the SCTD of 2D semiconductors and its application in electronic and optoelectronic devices.The underlying mechanism of STCD processes on 2D semiconductors is briefly introduced.Its impact on tuning the fundamental properties of various 2D systems is highlighted.We particularly emphasize on the SCTD-enabled high-performance 2D functional devices.Finally,the challenges and opportunities for the future development of SCTD are discussed.

Charge density wave phase suppression in 1T-TiSe_(2) through Sn intercalation

Taking advantage of the unique layered structure of TiSe2,the intrinsic electronic properties of two-dimensional materials can easily be tuned via heteroatomic engineering.Herein,we show that the charge density wave(CDW)phase in 1T-TiSe_(2) single-crystals can be gradually suppressed through Sn atoms intercalation.Using angle-resolved photoemission spectroscopy(ARPES)and temperature-dependent resistivity measurements,this work reveals that Sn atoms can induce charge doping and modulate the intrinsic electronic properties in the host 1T-TiSe_(2).Notably,our temperature-dependent ARPES results highlight the role exciton-phonon interaction and the Jahn-Teller mechanism through the formation of backfolded bands and exhibition of a downward Se shift of 4p valence band in the formation of CDW in this material.

Improving solar control of magnetism in ternary organic photovoltaic system with enhanced photo-induced electrons doping

§The growing demand for storage space has promoted in-depth research on magnetic performance regulation in an energy-saving way.Recently,we developed a solar control of magnetism,allowing the magnetic moment to be manipulated by sunlight instead of the magnetic field,current,or laser.Here,binary and ternary photoactive systems with different photon-to-electron conversions are proposed.The photovoltaic/magnetic heterostructures with a ternary system induce larger magnetic changes due to higher short current density(J SC)(20.92 mA·cm^(−2))compared with the binary system(11.94 mA·cm^(−2)).During the sunlight illumination,ferromagnetic resonance(FMR)shift increases by 80%(from 169.52 to 305.48 Oe)attributed to enhanced photo-induced electrons doping,and the variation of saturation magnetization(M S)is also amplified by 14%(from 9.9%to 11.3%).Furthermore,photovoltaic performance analysis and the transient absorption(TA)spectra indicate that the current density plays a major role in visible light manipulating magnetism.These findings clarify the laws of sunlight control of magnetism and lay the foundation for the next generation solar-driven magneto-optical memory applications.

Thickness-dependent enhanced optoelectronic performance of surface charge transfer-doped ReS2 photodetectors

Surface charge transfer doping has been widely utilized to tune the electronic and optical properties of semiconductor photodetectors based on low-dimensional materials.Although many studies have been conducted on the performance(response time,responsivity,etc.)of doped photodetectors and their mechanisms,they merely examined a specific thickness and did not systematically explore the dependence of doping effects on the number of layers.This work performs a series of investigations on ReS_(2)photodetectors with different numbers of layers and demonstrates that the p-dopant tetrafluorotetracyanoquinodimethane(F_(4)-TCNQ)converts the deep trap states into recombination centers for few-layer ReS_(2)and induces a vertical p-n junction for thicker ReS_(2).A response time of 200 ms is observed in the decorated 2-layer ReS_(2)photodetector,more than two orders of magnitude faster than the response of the pristine photodetector,due to the disappearance of deep trap states.A current rectification ratio of 30 in the F_(4)-TCNQ-decorated sandwiched ReS_(2)device demonstrates the formation of a vertical p-n junction in a thicker ReS_(2)device.The responsivity is as high as 2,000 A/W owing to the strong carrier separation of the p-n junction.Different thicknesses of ReS_(2)enable switching of the prominent operating mechanism between transforming deep trap states into recombination centers and forming a vertical p-n junction.The thicknessdependent doping effect of a two-dimensional material serves as a new mechanism and provides a scheme toward improving the performance of other semiconductor devices,especially optical and electronic devices based on low-dimensional materials.

Tune the photoresponse of monolayer MoS_(2) by decorating CsPbBr_(3) perovskite nanoparticles

Tuning the photoresponse of monolayer MoS_(2) could extend its potential application in many fields,however,it is still a challenge.In this study,CsPbBr_(3) nanoparticles were prepared and spin-coated on the surface of monolayer MoS_(2) to fabricate hybrid CsPbBr_(3)/MoS_(2) photodetectors.By combing the photoelectrical property of the CsPbBr_(3),the synergistic effect has been systematically studied from its carrier mobility,photoresponse and detectivity.It was found that nanofilm-coating of CsPbBr_(3)would impede the photoelectric performance due to the electron-hole recombination facilitated by the defects at the interface of C PbBr_(3) and MoS_(2) films.While the nanoparticles decorating was observed to significantly improve the conductivity of the monolayer Mo S_(2),which also increased the on/off ratio of the MoS_(2) transistor from 8.2×10~3 to 4.4×10^(4),and enhanced the carrier mobility from 0.090 cm^(2)V^(-1)s^(-1)to 0.202 cm^(2)V^(-1)s^(-1),ascribing to a mixed electron recombination-injection process.Furthermore,the CsPbBr_(3) nanofilm would decrease the responsivity to 136 and 178 A/W under the light wavelength of 400 and 500 nm,respectively,while decorating CsPbBr_(3) nanoparticles improve the photoresponse to 948 and 883 A/W with the detectivity at the level of 10^(11)Jones.This work may provide an easy and cost-efficient way to tune the photoresponse of MoS_(2) photodetectors.

Superconducting properties and topological nodal lines features in centrosymmetric Sn_(0.5)TaSe_(2)

Nontrivial topological behaviors in superconducting materials provide resourceful ground for the emergence and study of unconventional quantum states.Charge doping by the controlled intercalation of donor atoms is an efficient route for enhancing/inducement of superconducting and topological behaviors in layered topological insulators and semimetals.Herein,we enhanced the superconducting temperature of TaSe_(2) by 20-folds(~3 K)through Sn atoms intercalation.Using first-principles calculations,we demonstrated the existence of nontrivial topological features.Sn_(0.5)TaSe_(2) displays topological nodal lines around the K high symmetry point in the Brillouin zone,with drumhead-like shaped surface states protected by inversion symmetry.Altogether,the coexistence of these properties makes Sn_(0.5)TaSe_(2) a potential candidate for topological superconductivity.

Design and optimization of BCCD in CMOS technology

This paper optimizes the buried channel charge-coupled device(BCCD) structure fabricated by complementary metal oxide semiconductor(CMOS) technology. The optimized BCCD has advantages of low noise, high integration and high image quality. The charge transfer process shows that interface traps, weak fringing fields and potential well between adjacent gates all cause the decrease of charge transfer efficiency(CTE). CTE and well capacity are simulated with different operating voltages and gap sizes. CTE can achieve 99.999% and the well capacity reaches up to 25 000 electrons for the gap size of 130 nm and the maximum operating voltage of 3 V.