Lateral PtSe 2 p–n Homojunction Formation via Selective Surface Doping for Self-Powered Temperature Sensing

N-doped carbon nanomaterials (NCMs) have attracted significant interest as metal-free nanozymes for sensing due to their exceptional stability and biocompatibility. However, the controversial active sites and catalytic pathways severely hinder the application of NCM-based nanozymes. Here, postsynthetic modification methods have been developed to study the catalytic mechanism, including selective deactivation, chemical grafting, and surface doping. Model NCMs are synthesized through the direct pyrolysis of conjugated porous polymers, which exhibit remarkable oxidase-like activity. It has been demonstrated that the ortho-C atom of pyridinic-N serves as the active site for the O2 adsorption, while a moderate increase in graphitic-N can promote the interfacial electron transfer to enhance the oxidase-like activity. In contrast, the two N-doping types contribute to the peroxidase properties. Furthermore, the metal-free characteristic and enzyme-like activity of PTPAV-C render it an appropriate choice for the assay of total antioxidant capacity. The colorimetric sensor demonstrates excellent selectivity, as only reductive analytes induce significant color changes. These findings provide comprehensive insights into the catalytic mechanisms of NCMs, thereby enabling the rational design of enzyme mimics.

Lateral solid phase epitaxy (L-SPE) of amorphous Si (a-Si) films by a selective surface doping method of P atoms was investigated, in which P atoms were doped only in the surface layers of a-Si films. It was found that the L-SPE growth rate and the growth length from the seed region were changed by thickness of the P-doped layer, but they weakly depended on the thickness of the a-Si film. It was also found from cross-sectional transmission electron microscopy that the growth front of L-SPE in the surface P-doped sample was composed of a single facet. In order to explain these experimental results, a L-SPE growth model in the surface P-doped sample is proposed.

Atomic and electronic structures of the Ge(111) –Au surface with two metallic bands are studied by scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES). The bias-voltage-dependent periodic structure observed by STM is consistent with the electronic structure calculated for an optimized conjugate honeycomb chained trimer (CHCT) model. Electrons are selectively doped to the electron-like surface metallic band by excess Au atoms, which form triangle structures with the Au trimers of the CHCT model. The discrepancy for the bottom energy of the electron-like band between the ARPES results and those of the calculation is attributed to the doping. The triangle structure is mobile at room temperature, but stable at 80 K. Both Au and Ge atoms deposited at room temperature on the Ge(111) –Au surface dope electrons to the electron-like surface metallic band. Moreover, the Au atoms increase the spin–orbit interaction at the surface, and thus make the splitting of the spin-polarized band due to the interaction larger than that before the deposition.

Non-rectifying (ohmic) contacts are essential for efficient photoconductive semiconductor switch performance and maximizing breakdown voltage. Fabricating ohmic contacts requires a very heavily doped surface layer (> 1018 cm−3), and in silicon carbide (SiC) is typically done by ion implantation. The high energy ions from this process often cause surface and bulk damage, and a high temperature anneal is required to repair the crystal structure and activate the impurities. This paper investigates the use of a gas immersion laser enhanced diffusion system to selectively dope the SiC as an attractive, low cost alternative to ion implantation. A pulsed 260 nm laser with a peak irradiance of 69.9 MW/cm2 was used to dope a high purity semi-insulating (HPSI) 4H-SiC sample with nitrogen to a depth of 150 nm, with measured a surface concentration greater than 1020 cm−3. Using a one dimensional thermal model, the experimental data was fit to diffusion coefficients that are orders of magnitude greater than typically seen in SiC. The gas immersion laser doping technique has been demonstrated as a viable alternative to ion implantation for selective area doping of SiC bulk photoconductive switches.

We have used broadband synchrotron radiation to induce selective area surface doping of boron into silicon. The source of the boron was nido-decaborane (B10H14) adsorbed on Si(111) at 100 K. Irradiation caused decomposition of the adsorbed molecule which lead to an enhanced concentration of free boron in the irradiated area. Using Si 2p core level photoelectron spectroscopy, the surface chemical composition and Fermi level position in both the irradiated and unirradiated regions were determined. The downward movement of the Fermi level was greater in the irradiated region than in the unirradiated region, and greater for n-type than for p-type Si.

Fabrication and analysis of a 21% efficient baseline n-PERT cell in this paper revealed that its performance was limited by its large J 0 values on the front and back side, highlighting the need for a bifacial structure with selective emitters to decrease J 0 . To determine the practical efficiency limit of such a cell, Sentaurus 2-D modeling was conducted using doping profiles previously reported for high efficiency cells. The maximum efficiency was calculated to be 22.7% with self-alignment of the contacts to the heavily doped regions. Modeling was then conducted to investigate the losses incurred from the required alignment tolerances associated with the heavily doped region and metal contacts made with today's large-scale manufacturing equipment. Through careful design of the selective emitter and back surface field doping profiles, we show that for 50 μm wide metal contacts screen printed on a 300 μm wide heavily doped region on a 10 Ω-cm base wafer with bulk lifetime of 3 ms, the loss can be decreased by 0.65%, with practical screen-printed cell efficiencies approaching 22.5%. Projected future technology improvements show efficiencies up to 23% are possible with this structure.

Controlling N and C-atom densities in N2/H2 and N2/CH4 microwave afterglows for selective TiO2 surface nitriding

We explored the selective surface doping of anodically formed TiO2 nanotube arrays (TNTAs) with divalent Sr2+ cations using an electrochemical cathodization process in order to modify the basicity of the surface and modify the interactions of the surface with vapor phase CO2. The resulting Sr-doped TNTAs showed a 3-fold increase in CO2 photoreduction activity. Characterization using a broad suite of bulk- and surface-sensitive characterization techniques revealed the doped Sr atoms to be widely dispersed on the surface. Our results show a way forward to achieve single atom catalysts using cathodic doping of TiO2.

The state-of-the-art of Er-doped integrated optical devices in LiNbO/sub 3/ is reviewed starting with a brief discussion of the technology of Er-indiffusion. This technique yields high-quality waveguides and allows a selective surface doping necessary to develop optical circuits of higher complexity. Doped waveguides have been used as single- and double-pass optical amplifiers for the wavelength range 1530 nm</spl lambda/<1610 nm. If incorporated in conventional, lossy devices loss-compensating or even amplifying devices can be fabricated. Examples are an electrooptically scanned Ti:Er:LiNbO/sub 3/ waveguide resonator used as an optical spectrum analyzer and an acoustooptically tunable filter used as a tunable narrowband amplifier. Different types of Ti:Er:LiNbO/sub 3/ waveguide lasers are presented. Among them are free running Fabry-Perot lasers for six different wavelengths with a continuous-wave (CW)-output power up to 63 mW. Tunable lasers could be demonstrated by the intracavity integration of an acoustooptical amplifying wavelength filter yielding a tuning range up to 31 nm. With intracavity electrooptic phase modulation modelocked laser operation has been obtained with pulse repetition frequencies up to 10 GHz; pulses of only a few ps width could be generated. With intracavity amplitude modulation Q-switched laser operation has been achieved leading to the emission of pulses of up to 2.4 W peak power (0.18 /spl mu/J) at 2 kHz repetition frequency. Distributed Bragg reflector (DBR) lasers of emission linewidth /spl les/8 kHz have been developed using a dry-etched surface grating as one of the mirrors of the laser resonator. Finally, as an example for a monolithic integration of lasers and extracavity devices on the same substrate, a DBR-laser/modulator combination is presented.

Spontaneous passivation on high-voltage manganese-based layered oxide cathodes via selective surface doping for potassium-ion batteries

Growth characteristics and device application of the selective surface doping method in lateral solid phase epitaxy (L-SPE) are presented. In this method, P atoms are incorporated near the surface of amorphous Si (a-Si) films to enhance the L-SPE growth and the underlying undoped layers are used for device fabrication. First, the growth characteristics are investigated by changing thicknesses of the a-Si film and the P-doped layer, and a quantitative model to explain the experimental results is presented. Then, it is shown that redistribution of the P atoms during L-SPE annealing is negligibly small, and the P-doped layer is selectively etched by combination of a wet chemical etchant and subsequent reactive ion etching. Finally, metal-oxide-semiconductor field-effect transistors (MOSFETs) with upper and lower gate electrodes are fabricated in the undoped layer and the electrical properties of both the upper and lower channel FETs are investigated.

Self-powered temperature and humidity sensing platform based on Ag2S/poly(5-carboxyindole)/hydroxyethyl cellulose nanocomposite.

Emergence of multiple negative differential transconductance from a WSe2 double lateral homojunction platform

In this work, the operation of n- and p-type field-effect transistors (FETs) on the same WSe2 flake is realized,and a complementary logic inverter is demonstrated. The p-FET is fabricated by contacting WSe2 with a high work function metal, Pt, which facilities hole injection at the source contact. The n-FET is realized by utilizing selective surface charge transfer doping with potassium to form degenerately doped n+ contacts for electron injection. An ON/OFF current ratio of >10(4) is achieved for both n- and p-FETs with similar ON current densities. A dc voltage gain of >12 is measured for the complementary WSe2 inverter. This work presents an important advance toward realization of complementary logic devices based on layered chalcogenide semiconductors for electronic applications.

Thermoelectric (TE) effect based temperature sensor can accurately convert temperature signal into voltage without external power supply, which have great application prospects in self-powered temperature electronic skin (STES). But the fabrication of stretchable and distributed STES still remains a challenge. Here, a novel STES design strategy is proposed by combining flexible island-bridge structure with BiTe-based micro-thermoelectric generator (µ-TEG). Furthermore, a 4×4 vertical temperature sensor array with good stretchability and distributed sensing property has been fabricated for the first time. The interfacial chemical bonds located between the rigid islands (µ-TEG) and the flexible substrate (polydimethylsiloxane, PDMS) endow the STES with excellent stretchability, and its sensing performance remains unchanged under 30% strain (the maximum strain of human skin). Moreover, the STES sensing unit possesses high sensitivity (729 µV K-1 ), rapid response time (0.157 s), and high spatial resolution (2.75×2.75 mm2 ). As a proof of concept, this work demonstrates the application of the STES in the detection of mini-region heat sources in various scenarios including noncontact spatial temperature responsing, intelligent robotic thermosensing, and wearable temperature sensing. Such an inspiring design strategy is expected to provide guidance for the design and fabrication of wearable self-powered temperature sensors.