Simultaneously optimizing performances, processability and fabrication cost of organic electronic materials is the continual source of compromise hindering the development of disruptive applications. In this work, we identified a strategy to achieve record conductivity values of one of the most benchmarked semiconducting polymers by doping with an entirely solution-processed, water-free and cost-effective technique. High electrical conductivity for poly(3-hexylthiophene) up to 21 S/cm has been achieved, using a commercially available electron acceptor as both a Lewis acid and an oxidizing agent. While we managed water-free solution-processing a three-time higher conductivity for P3HT with a very affordable/available chemical, near-field microscopy reveals the existence of concentration-dependent higher-conductivity micro-domains for which furthermore process optimization might access to even higher performances. In the perpetual quest of reaching higher performances for organic electronics, this work shall greatly unlock applications maturation requiring higher-scale processability and lower fabrication costs concomitant of higher performances and new functionalities, in the current context where understanding the doping mechanism of such class of materials remains of the greatest interest.
Doping of semiconductors is essential in modern electronic and photonic devices. While doping is well understood in bulk semiconductors, the advent of carbon nanotubes and nanowires for nanoelectronic and nanophotonic applications raises some key questions about the role and impact of doping at low dimensionality. Here we show that for semiconducting carbon nanotubes, bandgaps and exciton binding energies can be dramatically reduced upon experimentally relevant doping, and can be tuned gradually over a broad range of energies in contrast to higher dimensional systems. The later feature is made…
RuGe, a diamagnetic small-band gap semiconductor, and CoGe, a nonmagnetic semimetal, are both isostructural to the Kondo insulator FeSi and the skyrmion lattice host MnSi. Here, we have explored the magnetic and transport properties of Co-doped RuGe: Ru$_{1-x}$Co$_x$Ge. For small values of $x$, a magnetic ground state emerges with $T_{c}\approx$ 5 $-$ 9 K, which is accompanied by a moderate decrease in electrical resistivity and a Seebeck coefficient that indicates electron-like charge carriers. The magnetization, magnetoresistance, and the specific heat capacity all resemble that of Fe$_{1-x}…
Novel or unusual magnetism is a subject of considerable interest, particularly in metals and degenerate semiconductors. In such materials the interplay of magnetism, transport and other Fermi liquid properties can lead to fascinating physical behavior. One example is in magnetic semiconductors, where spin polarized currents may be controlled and used. We report density functional calculations predicting magnetism in doped semiconducting beta-FeSi2 and CrSi2 at relatively low doping levels particularly for n-type. In this case, there is a rapid cross-over to a half-metallic state as a function …
Graphene nanomeshes (GNM's) formed by the creation of pore superlattices in graphene, are a possible route to graphene-based electronics due to their semiconducting properties, including the emergence of fractional eV band gaps. The utility of GNM's would be markedly increased if a scheme to stably and controllably dope them was developed. In this work, a chemically-motivated approach to GNM doping based on selective pore-perimeter passivation and subsequent ion chelation is proposed. It is shown by first-principles calculations that ion chelation leads to stable doping of the passivated GNM's…
We report here metal to insulator transition, colossal Seebeck coefficient and ultralow thermal conductivity (0.0057th of its bulk value, significantly smaller than many well-known thermoelectric materials and silicon, showing potential applications in thermoelectrics, electronics and photonics for heat dissipation) in monodispersed well characterized Ni nanoparticles. As a consequence, thermoelectric power factor and figure of merit are significantly enhanced compared to their bulk counterpart. Interestingly, a systematic crossover from metallic to semiconducting to finally electrically insul…
Ultrananocrystalline diamond/hydrogenated amorphous carbon composite thin films synthesized via coaxial arc plasma possess a marked structural feature of diamond grains embedded in an amorphous carbon and a hydrogenated amorphous carbon matrix which are the largest constituents of the films. Since the amorphous nature yields much larger light absorption coefficients as well as a generation source of photo-induced carriers with UV rays, these films can be potential candidates for deep-UV photodetector applications. From some previous studies p-type conduction of the films has been realized by d…
We report on infrared (IR) absorption and dc electrical measurements of thin films of poly(3-hexylthiophene) (P3HT) that have been modified by a fluoroalkyl trichlorosilane (FTS). Spectra for FTS-treated films were compared to data for electrostatically-doped P3HT in an organic field-effect transistor (OFET). The appearance of a prominent polaron band in mid-IR absorption data for FTS-treated P3HT supports the assertion of hole doping via a charge-transfer process between FTS molecules and P3HT. In highly-doped films with a significantly enhanced polaron band, we find a monotonic Drude-like ab…
We present a first-principles study of semiconducting carbon nanotubes adsorbed on the unpassivated Si(100) surface. We have found metallicity for the combined system caused by n-doping of the silicon slab representing the surface by the SWNT. We confirm this metallicity for nanotubes of different diameters and chiral angles, and find the effect to be independent of the orientation of the nanotubes on the surface. We also present adsorption energetics and configurations which show semiconducting SWNTs farther apart from the surface and transferring less charge, in comparison with metallic SWNT…
We study the organic electrochemical transistors (OECTs) performance of the ladder polymer, poly(benzimidazobenzophenanthroline) (BBL) in an attempt to better understand how an apparently hydrophobic side-chain-free polymer is able to operate as an OECT with favorable redox kinetics in an aqueous environment. We examine two BBLs of different molecular masses from different sources. Both BBLs show significant film swelling during the initial reduction step. By combining electrochemical quartz crystal microbalance (eQCM) gravimetry, in-operando atomic force microscopy (AFM), and both ex-situ and…
Crystalline Si substrates are doped by laser annealing of solution processed Si. For this experiment, dispersions of highly B-doped Si nanoparticles (NPs) are deposited onto intrinsic Si and laser processed using an 807.5nm cw-laser. During laser processing the particles as well as a surface-near substrate layer are melted to subsequently crystallize in the same orientation as the substrate. The doping profile is investigated by secondary ion mass spectroscopy revealing a constant B concentration of 2x10^18 cm^-3 throughout the entire analyzed depth of 5μm. Four-point probe measurements demons…
Scandium nitride (ScN) is a semiconducting transition metal nitride for which there are not identified dopants. We present local density functional calculations, in supercell approach, for ScN doped with O and C in N-sites and Ca and Ti in Sc-sites. Small additions of these atoms have the effect of shifting the Fermi level within the electronic band structure. O and Ti bring occupied states in bottom of conduction band, while C and Ca produces holes in top of valence band. Based on the theory we propose that bipolar doping is possible to scandium nitride.
The implementation of graphene in semiconducting technology requires the precise knowledge about the graphene-semiconductor interface. In our work the structure and electronic properties of the graphene/$n$-Ge(110) interface are investigated on the local (nm) and macro (from $μ\mathrm{m}$ to mm) scales via a combination of different microscopic and spectroscopic surface science techniques accompanied by density functional theory calculations. The electronic structure of freestanding graphene remains almost completely intact in this system, with only a moderate $n$-doping indicating weak intera…
p-type doping from the dielectric/semiconductor interface of a SnO2 thin film transistor (TFT) has been utilized to develop high carrier mobility balanced ambipolar oxide-transistor. To introduce this interfacial-doping, bottom-gate top-contact TFTs have been fabricated by using two different ion-conducting oxide dielectrics which contain trivalent atoms. These ion-conducting dielectrics are LilnO2 and LiGaO2 respectively, containing mobile Li+ ion. During SnO2 thin film fabrication on top of the ionic dielectric, those trivalent atoms allow p- doping to the interfacial SnO2 layer to introduce…
An ab initio study of the electronic structures of solid metallotetrabenzoporphyrins (MTBPs) utilized in organic transistors and photovoltaics is presented. Bandstructures, densities of states, and orbitals are calculated for H2, Cu, Ni, and Zn core substitutions of the unit cell of solid TBP, as deposited via soluble precursors that are thermally annealed to produce polycrystalline, semiconducting thin-films. While the unit cells of the studied MTBPs are nearly isomorphous, substitution of the core atoms alters the structure of the bands around the energy bandgap and the composition of the de…
Stanene is a quantum spin hall insulator and a promising material for electronic and optoelectronic devices. Density functional theory (DFT) calculations are performed to study the band gap opening in stanene by elemental mono- (B, N) and co-doping (B-N). Different patterned B-N co-doping is studied to change the electronic properties in stanene. A patterned B-N co-doping opens the band gap in stanene and the semiconducting nature persists with strain. Molecular dynamics (MD) simulations are performed to confirm the thermal stability of such doped system. The stress-strain study indicates that…
Motivated by the ongoing interest in nitrides as materials for spintronics applications we have studied effects of doping with magnetic transition-metal elements (T=Cr,Mn,Fe,Co and Ni) on the electronic properties of semiconducting scandium nitride. Using density functional together with the generalized gradient approximation (GGA) as well as PBE0r hybrid functional (with different mixing of the exact exchange), two different doping amounts 25\% ($\rm Sc_{0.75}T_{0.25}N$) and 10\% ($\rm Sc_{0.9}T_{0.1}N$) have been investigated. This is done in comparison to the reference compound ScN with a s…
The emergence of semiconducting materials with inert or dangling bond-free surfaces has created opportunities to form van der Waals heterostructures without the constraints of traditional epitaxial growth. For example, layered two-dimensional (2D) semiconductors have been incorporated into heterostructure devices with gate-tunable electronic and optical functionalities. However, 2D materials present processing challenges that have prevented these heterostructures from being produced with sufficient scalability and/or homogeneity to enable their incorporation into large-area integrated circuits…
Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) and black phosphorus (BP) have beneficial electronic, optical, and physical properties at the few-layer limit. As atomically thin materials, 2D TMDCs and BP are highly sensitive to their environment and chemical modification, resulting in a strong dependence of their properties on substrate effects, intrinsic defects, and extrinsic adsorbates. Furthermore, the integration of 2D semiconductors into electronic and optoelectronic devices introduces unique challenges at metal-semiconductor and dielectric-semiconductor int…
Atomic intercalation in two dimensional (2D) layered materials can engineer the electronic structure at the atomic scale, bringing out tunable physical and chemical properties which are quite distinct in comparison with pristine one. Among them, electron-doped engineering induced by intercalation is an efficient route to modulate electronic states in 2D layers. Herein, we demonstrate a semiconducting to the metallic phase transition in zirconium diselenide (ZrSe2) single crystal via controllable incorporation of copper (Cu) atoms. Combined with first-principles density functional theory (DFT) …
A novel and direct method is proposed to assess the doping limits of semiconducting materials. Applied to the case of ZnO, our first-principles calculations demonstrate that p-type ZnO is thermodynamically unstable.
This work reports on temperature-induced out-diffusion and concentration decay of the prominent intrinsic point defect VNi (nickel vacancy) in the wide-gap p-type semiconductor nickel oxide (NiO). VNi can easily be introduced into NiO thin films by offering high oxygen partial pressures during film growth, rendering nonstoichiometric semiconducting structures. However, exposure to lower oxygen supply after growth, e.g. in a standard atmosphere, usually leads to a gradual decrease of film conductivity, because the vacancy concentration equilibrates. In this study, we observe this process in sit…
The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowi…
Dilute magnetic semiconductors, achieved through substitutional doping of spin-polarized transition metals into semiconducting systems, enable experimental modulation of spin dynamics in ways that hold great promise for novel magneto-electric or magneto-optical devices, especially for two-dimensional systems such as transition metal dichalcogenides that accentuate interactions and activate valley degrees of freedom. Practical applications of 2D magnetism will likely require room-temperature operation, air stability, and (for magnetic semiconductors) the ability to achieve optimal doping levels…
For high efficiency thermoelectric power conversion not only improvement of materials properties but also prediction and synthesis of new thermoelectric materials is needed. Here we have carried out a systematic investigation on thermoelectric performance of newly predicted two dimensional (2D) semiconducting SiS2 and SiSe2 monolayers of group IVA-VIA family using density functional theory (DFT) and Boltzmann transport equation (BTE). Our computed values of lattice thermal conductivity (kph) are ultralow which result very high thermoelectric figure of merit (ZT) value of 0.78 (0.80) at 500K in…
Two-dimensional (2D) ferromagnetic (FM) semiconductors with high Curie temperature have long been pursued for electronic and spintronic applications. Here we provide a general strategy to achieve robust FM state in bilayer CrI3 of the monoclinic stacking, which intrinsically has interlayer antiferromagnetic (AFM) order and weak in-plane FM coupling. We showed that the proximity effect from bulk semiconducting substrates induces electronic doping and significantly increases the FM nearest-neighbor exchange for bilayer CrI3, leading to the AFM-to-FM transition for the interlayer spin configurati…
Two-dimensional (2D) transition metal dichalcogenides (TMDs) have recently emerged as promising candidates for future electronics and optoelectronics. While most of TMDs are intrinsic n-type semiconductors due to electron donating which originates from chalcogen vacancies, obtaining intrinsic high-quality p-type semiconducting TMDs has been challenging. Here, we report an experimental approach to obtain intrinsic p-type Tungsten (W)-based TMDs by substitutional Ta-doping. The obtained few-layer Ta-doped WSe2 (Ta0.01W0.99Se2) field-effect transistor (FET) devices exhibit competitive p-type perf…
Solution processed polymers are at the core of organic electronics. Polyradicals (polymers in which each repeating unit contains an unpaired spin) are unique alternatives to their p-conjugated, semiconducting counterparts. Unique of polyradicals are tunable charge states localized at their repeating units, which enable electrically switchable charge transport regimes. Tremendous efforts were focused on polyradical memristors and batteries. Notwithstanding recent progress in doping, polyradical field-effect transistors (PR-FETs) have not been reported. Here, we show that vertical architectures,…
Many properties of layered materials change as they are thinned from their bulk forms down to single layers, with examples including indirect-to-direct band gap transition in 2H semiconducting transition metal dichalcogenides as well as thickness-dependent changes in the valence band structure in post-transition metal monochalcogenides and black phosphorus. Here, we use angle-resolved photoemission spectroscopy to study the electronic band structure of monolayer ReSe$_{2}$, a semiconductor with a distorted 1T structure and in-plane anisotropy. By changing the polarization of incoming photons, …
Controlling doping is essential for a successful integration of semiconductor materials into device technologies. However, the assessment of doping levels and the distribution of charge carriers in carbon nanotubes or other nanoscale semiconductor materials is often either limited to a qualitative attribution of being 'high' or 'low' or it is entirely absent. Here, we describe efforts toward a quantitative characterization of doping in redox- or electrochemically doped semiconducting carbon nanotubes (s-SWNTs) using VIS-NIR absorption spectroscopy. We discuss how carrier densities up to about …
Anisotropic magnetic and electronic transport measurements were carried out on large single crystals of Fe1-xCoxSb2 (0<= x <=1). The semiconducting state of FeSb2 evolves into metallic and weakly ferromagnetic by substitution of Fe with Co for x<0.5. Further doping induces structural transformation from orthorhombic Pnnm structure of FeSb2 to monoclinic P21/c structure of CoSb2 where semiconducting and diamagnetic ground state is restored again. Large magnetoresistance and anisotropy in electronic transport were observed.
Quantum confined Au nanoclusters exhibit molecule-like properties, including atomic precision and discrete energy levels. The electrical conductivity of Au nanocluster films can vary by several orders of magnitude, and is determined by the strength of the electronic coupling between the individual nanoclusters in the film. Similar to quantum confined, semiconducting quantum dots, the electrical coupling in films is dependent on the size and structure of the Au core and the length and conjugation of the organic ligands surrounding it. Unlike quantum dots, however, semiconducting transport has n…
(Ga,Mn)As is at the forefront of research exploring the synergy of magnetism with the physics and technology of semiconductors, and has led to discoveries of new spin-dependent phenomena and functionalities applicable to a wide range of material systems. Its recognition and utility as an ideal model material for spintronics research has been undermined by the large scatter in reported semiconducting doping trends and micromagnetic parameters. In this paper we establish these basic material characteristics by individually optimizing the highly non-equilibrium synthesis for each Mn-doping level …
We have investigated the Co-doping dependence of the structural, transport, and magnetic properties of ε-FeCoSi epilayers grown by molecular beam epitaxy on silicon (111) substrates. Low energy electron diffraction, atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy studies have confirmed the growth of phase-pure, defect-free ε-FeCoSi epitaxial films with a surface roughness of ~1 nm. These epilayers are strained due to lattice mismatch with the substrate, deforming the cubic B20 lattice so that it becomes rhombohedral. The temperature dependence o…
Dirac and Weyl nodal materials can host low-energy relativistic quasiparticles. Under strong magnetic fields, the topological properties of Dirac/Weyl materials can directly manifest through quantum Hall states. However, most Dirac/Weyl nodes generically exist in semimetals without exploitable bandgaps due to their accidental band-crossing origin. Here we report the first experimental observation of Weyl fermions in a semiconductor. Tellurene, the 2D form of tellurium, possesses chiral crystal structure which induces unconventional Weyl nodes with a hedgehog-like radial spin texture near the c…
Density functional methods have been used to study the crystal, electronic and magnetic structures of new ordered double perovskites A2NRuO6 (A2 = Ba2, BaLa; N = V, Cr, Fe). In the doped compounds, the A-site was replaced by 1:1 of Ba and La cations, BaLaNRuO6. All compounds of A2NRuO6 crystallize in cubic symmetry with space group Fm-3m and tilt system a0a0a0. The electronic and magnetic calculations were performed by the full-potential linear muffin-tin orbital method using both the generalized gradient approximation and GGA plus on-site electron correlation effect GGA+U. In GGA, Ba2NRuO6 sh…
We report a combined theoretical and experimental search for thermoelectric materials based on semiconducting zinc antimony. Influence of three new doping elements (sodium, potassium and boron) on the electronic properties is investigated as well as the carrier concentration and temperature dependence of the thermoelectric coefficients obtained through density-functional calculations and Boltzmann transport theory. Distortion of the electron arrangement caused by the doping elements is displayed as a deformation charge density around the atoms. Based on the band structures, the density of stat…
Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviours, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use dopi…
SnSe is a promising thermoelectric material with record-breaking figure of merit, \textit{i.e., ZT}. As a semiconductor, optimal electrical dosage is the key challenge to maximize \textit{ZT} in SnSe. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole doping mechanism in SnSe is still absent. Here, we report the highly anisotropic electronic structure of SnSe investigated by both angle-resolved photoemission spectroscopy and quantum transport, in which a unique "\textit{pudding-mold}" shaped valence band with quasi-linear energy disper…
The control on the distribution of magnetic ions into a semiconducting host is crucial for the functionality of magnetically doped semiconductors. Through a structural analysis at the nanoscale, we give experimental evidence that the aggregation of Fe ions in (Ga,Fe)N and consequently the magnetic response of the material are affected by growth rate and co-doping with shallow impurities.
We present a study on the mechanical configuration and the electronic properties of semiconducting carbon nanotubes supported by partially depassivated silicon substrates, as inferred from topographic and spectroscopic data acquired with a room-temperature ultrahigh vacuum scanning tunneling microscope and density-functional theory calculations. A mechanical distortion and doping for semiconducting carbon nanotubes on Si(100)-(2x1):H with hydrogen-depassivated stripes up to 100 Angstrom wide are ascertained from both experiment and theory. The results presented here point towards novel and loc…
Finding proper electrocatalysts capable of efficient catalyzing both ORR and OER is of great importance for metal-air batteries. With increasing inclination towards structural and flexible devices, developing a high-performance self-standing air-cathode is highly demanded and challenging, as most of oxygen catalysts are powder and need to be further processed. Here, we construct highly bifunctional air catalyst from macroscopic CNT fibers (CNTf) through direct CVD spinning followed by hydrothermal method. The electrocatalytic properties of the samples were tuned by altering nitrogen-doping and…
BN Doping in the Realm of Two-Dimensional Fullerene Network for Unparalleled Structural, Electronic, Optical, and HER Advancements: A Cutting-Edge DFT Investigation
The semimetallic or semiconducting nature of the transition metal dichalcogenide 1$T$-TiSe$_2$ remains under debate after many decades mainly due to the fluctuating nature of its 2 $\times$ 2 $\times$ 2 charge-density-wave (CDW) phase at room-temperature. In this letter, using angle-resolved photoemission spectroscopy, we unambiguously demonstrate that the 1$T$-TiSe$_2$ normal state is semimetallic with an electron-hole band overlap of $\sim$110 meV by probing the low-energy electronic states of the perturbed CDW phase strongly doped by alkali atoms. Our study not only closes a long-standing d…
