Few-Layer MoS₂ p-Type Devices Enabled by Selective Doping Using Low Energy Phosphorus Implantation

P-type doping of MoS2 has proved to be a significant bottleneck in the realization of fundamental devices such as p-n junction diodes and p-type transistors due to its intrinsic n-type behavior. We report a CMOS compatible, controllable and area selective phosphorus plasma immersion ion implantation (PIII) process for p-type doping of MoS2. Physical characterization using SIMS, AFM, XRD and Raman techniques was used to identify process conditions with reduced lattice defects as well as low surface damage and etching, 4X lower than previous plasma based doping reports for MoS2. A wide range of nondegenerate to degenerate p-type doping is demonstrated in MoS2 field effect transistors exhibiting dominant hole transport. Nearly ideal and air stable, lateral homogeneous p-n junction diodes with a gate-tunable rectification ratio as high as 2 × 10(4) are demonstrated using area selective doping. Comparison of XPS data from unimplanted and implanted MoS2 layers shows a shift of 0.67 eV toward lower binding energies for Mo and S peaks indicating p-type doping. First-principles calculations using density functional theory techniques confirm p-type doping due to charge transfer originating from substitutional as well as physisorbed phosphorus in top few layers of MoS2. Pre-existing sulfur vacancies are shown to enhance the doping level significantly.

Association of B12 deficiency and clinical neuropathy with metformin use in type 2 diabetes patients

CONTEXT

Long-term metformin use has been hypothesized to cause B12 deficiency and neuropathy in Type 2 diabetes patients. However, there is a paucity of Indian data regarding the same.

AIM

To compare the prevalence of B12 deficiency and peripheral neuropathy in patients with Type 2 diabetes mellitus treated with or without metformin.

MATERIALS AND METHODS

We recruited patients with Type 2 diabetes and divided them into metformin exposed and nonmetformin exposed groups. We measured baseline demographic variables like age, sex, vegetarian status, and HbA1c levels in both groups. We compared vitamin B12 levels and severity of peripheral neuropathy (using Toronto Clinical Scoring System (TCSS)) in both groups. Definite B12 deficiency was defined as B12 <150 pg/ml and possible B12 deficiency as <220 pg/ml. The difference in vitamin B12 levels and TCSS was calculated in both groups using independent samples t-test. Spearman's rank correlation between cumulative metformin use and B12 level was calculated. Odds ratio of vitamin B12 deficiency in metformin exposed group was also estimated.

RESULTS

Mean serum B12 levels was significantly lower in metformin exposed group (n=84) compared with nonmetformin exposed group (n=52) (410±230.7 versus 549.2±244.7, P=0.0011). Mean neuropathy score was significantly higher in metformin exposed group. (5.72±2.04 versus 4.62±2.12, P=0.0064). Odds ratio for possible B12 deficiency was 4.45 (95% CI 1.24-15.97). There was significant negative correlation between cumulative metformin dose and vitamin B12 level (r=-0.68, P<0.0001).

CONCLUSION

Metformin use is associated with vitamin B12 deficiency and clinical neuropathy in Type 2 diabetes patients.

Interfacial n-Doping Using an Ultrathin TiO2 Layer for Contact Resistance Reduction in MoS2

We demonstrate a low and constant effective Schottky barrier height (ΦB ∼ 40 meV) irrespective of the metal work function by introducing an ultrathin TiO2 ALD interfacial layer between various metals (Ti, Ni, Au, and Pd) and MoS2. Transmission line method devices with and without the contact TiO2 interfacial layer on the same MoS2 flake demonstrate reduced (24×) contact resistance (RC) in the presence of TiO2. The insertion of TiO2 at the source-drain contact interface results in significant improvement in the on-current and field effect mobility (up to 10×). The reduction in RC and ΦB has been explained through interfacial doping of MoS2 and validated by first-principles calculations, which indicate metallic behavior of the TiO2-MoS2 interface. Consistent with DFT results of interfacial doping, X-ray photoelectron spectroscopy (XPS) data also exhibit a 0.5 eV shift toward higher binding energies for Mo 3d and S 2p peaks in the presence of TiO2, indicating Fermi level movement toward the conduction band (n-type doping). Ultraviolet photoelectron spectroscopy (UPS) further corroborates the interfacial doping model, as MoS2 flakes capped with ultrathin TiO2 exhibit a reduction of 0.3 eV in the effective work function. Finally, a systematic comparison of the impact of selective doping with the TiO2 layer under the source-drain metal relative to that on top of the MoS2 channel shows a larger benefit for transistor performance from the reduction in source-drain contact resistance.

Sensitized ZnO nanorod assemblies to detect heavy metal contaminated phytomedicines: spectroscopic and simulation studies

The immense pharmacological relevance of the herbal medicine curcumin including anti-cancer and anti-Alzheimer effects, suggests it to be a superior alternative to synthesised drugs. The diverse functionalities with minimal side effects intensify the use of curcumin not only as a dietary supplement but also as a therapeutic agent. Besides all this effectiveness, some recent literature reported the presence of deleterious heavy metal contaminants from various sources in curcumin leading to potential health hazards. In this regard, we attempt to fabricate ZnO based nanoprobes to detect metal conjugated curcumin. We have synthesized and structurally characterized the ZnO nanorods (NR). Three samples namely curcumin (pure), Zn-curcumin (non-toxic metal attached to curcumin) and Hg-curcumin (toxic heavy metal attached to curcumin) were prepared for consideration. The samples were electrochemically deposited onto ZnO surfaces and the attachment was confirmed by cyclic voltammetry experiments. Moreover, to confirm a molecular level interaction picosecond-resolved PL-quenching of ZnO NR due to Förster Resonance Energy Transfer (FRET) from donor ZnO NR to the acceptor curcumin moieties was employed. The attachment proximity of ZnO NR and curcumin moieties depends on the size of metals. First principles analysis suggests a variance of attachment sites and heavy metal Hg conjugated curcumin binds through a peripheral hydroxy group to NR. We fabricated a facile photovoltaic device consisting of ZnO NR as the working electrode with Pt counter electrode and iodide-triiodide as the electrolyte. The trend in photocurrent under visible light illumination suggests an enhancement in the case of heavy metal ions due to long range interaction and greater accumulation of charge at the active electrode. Our results provide a detailed physical insight into interfacial processes that are crucial for detecting heavy-metal attached phytomedicines and are thus expected to find vast application as sensors for the detection of selective metal contaminants.

Cystic schwannoma of the pelvis

Schwannomas are benign tumours that arise from the Schwann cells of nerve fibres. They commonly occur in the head and neck, mediastinum and extremities. They are extremely rare in the pelvis. These are usually slow-growing tumours and are often detected incidentally. Preoperative diagnosis is extremely difficult as there are no definitive signs on imaging. Aspiration biopsy is often inconclusive or misleading. Surgical excision is both diagnostic and therapeutic. As these tumours are often large in size, open excision is most commonly performed. We describe a case of a large, cystic schwannoma of the pelvis causing bladder outlet obstruction and bilateral hydroureteronephrosis. Complete surgical excision was performed laparoscopically.

What can we learn from the vaginal mesh story?

The use of vaginal mesh in prolapse surgery has created enormous controversy and unprecedented media interest; it has become the most emotive topic in urogynecology today. The US Food and Drug Administration 510(k) system allowed the proliferation of mesh products which were rapidly adopted by surgeons internationally. The importance of a firm understanding of the biomechanical properties of tissue and implants, surgical skill, patient selection, communication skills, informed consent, and high-quality research are all important lessons we can learn from the mesh story. These lessons need to be applied to all novel treatments in the field of urogynecology and beyond.

All-Electrical High-Sensitivity, Low-Power Dual-Mode Gas Sensing and Recovery with a WSe2/MoS2 pn Heterodiode

Two-dimensional MoS₂ gas sensors have conventionally relied on a change in field-effect-transistor (FET) channel resistance or in the Schottky contact/pn homojunction barrier. We demonstrate an enhancement in sensitivity (6×) and dynamic response along with a reduction in detection limit (8×) and power (10⁴×) in a gate-tunable type-II WSe₂(p)/MoS₂(n) heterodiode gas sensor over an MoS₂ FET on the same flake. Measurements for varying NO₂ concentration, gate bias, and MoS₂ flake thickness, reinforced with first-principles calculations, indicate dual-mode operation due to (i) a series resistance-based exponential change in the high-bias thermionic current (high sensitivity), and (ii) a heterointerface carrier concentration-based linear change in near-zero-bias interlayer recombination current (low power) resulting in sub-100 μW/cm² power consumption. Fast and gate-bias tunable recovery enables an all-electrical, room-temperature dynamic operation. Coupled with the sensing of trinitrotoluene (TNT) molecules down to 80 ppb, this study highlights the potential of the WSe₂/MoS₂ pn heterojunction as a simple, low-overhead, and versatile chemical-sensing platform.

Extraperitoneal uterosacral suspension technique for post hysterectomy apical prolapse in 472 women: results from a longitudinal clinical study

OBJECTIVES

The study aims to evaluate the long-term results of the extraperitoneal uterosacral ligament suspension (bilateral) technique in women with apical prolapse following hysterectomy.

DESIGN

Longitudinal clinical follow up conducted between June 2002 and December 2017.

SETTING

Tertiary urogynaecology centre in Melbourne, Australia.

POPULATION

A total of 472 women with symptomatic vault prolapse who underwent bilateral extraperitoneal uterosacral ligament suspension (EPUSLS). Of these patients, 61% (287/472) had previously had a procedure for pelvic organ prolapse (POP).

METHODS

Follow up using structured, standardised questionnaires and examination by POP-Q and Baden-Walker system pre- and postoperatively.

MAIN OUTCOME MEASURES

Functional and anatomical results and surgical complications.

RESULTS

Mean follow-up duration was approximately 5 years. The objective success rate at vaginal cuff support was 89% (420/472). Only 4% needed revision surgery for vault recurrence. There was improvement in bladder, bowel, and sexual symptoms after the procedure. Mesh exposure rate was 17% (of the 138 having mesh augmentation), with the majority of cases managed conservatively or with minor interventions. The ureteric injury rate was 1% and mainly occurred in patients operated early on in the series. No women had buttock pain.

CONCLUSION

EPUSLS is an effective, suture-based procedure for vault prolapse with few complications even on long-term follow up. This technique avoids the need to open the peritoneum vaginally and has a low risk of ureteric injury and gluteal pain.

TWEETABLE ABSTRACT

Bilateral extraperitoneal USL suspension of vault is effective with low morbidity and a high success rate.

A combined spectroscopic and ab initio study of the transmetalation of a polyphenol as a potential purification strategy for food additives

Recently, metal exchange (transmetalation) techniques have become popular for the post-synthesis modification of metal organic complexes (MOCs). Here, we have explored the possibility of toxic metal ion (mercury (Hg)) exchange from a model polyphenol, curcumin, which is a very important food additive, using a much less toxic counterpart (copper). While the attachment of different metals on the polyphenol was confirmed using a picosecond resolved fluorescence technique, the surface plasmon resonance (SPR) band of the Ag nanoparticle (NP) was employed as a tool to detect uncoupled Hg ions in aqueous media. Furthermore, a microscopic understanding of the experimental observations was achieved through density functional theory (DFT) based theoretical studies. The presence of Cu ions in the vicinity of Hg-curcumin, upon ground state optimization, was observed to extrude most of the Hg from the curcumin complex and replace its position in the complex. The study may find relevance in the development of a purification strategy for food additives heavily contaminated with toxic metals.

High pressure structural and vibrational properties of the spin-gap system Cu2PO4(OH)

The structural and vibrational properties of the spin-gapped system Cu(2)PO(4)(OH) have been investigated at room temperature under high pressure up to ~20 GPa by Raman scattering and synchrotron-based x-ray diffraction and infrared (IR) spectroscopic measurements. The orthorhombic phase (space group Pnnm, z = 4) remains stable up to at least 7 GPa where it undergoes a weakly first order structural transition (with negligible volume drop) to a monoclinic phase (space group P2(1)/n, z = 4) with an abrupt monoclinic distortion. Refinement of atomic positions has been performed for the low pressure phase. The conspicuous changes in the vibrational spectra (Raman as well as far-IR) confirm this phase transition. At further higher pressures the monoclinic angle increases rapidly and the system transforms irreversibly into a disordered phase. Detailed vibrational analyses have been performed in the orthorhombic phase and pressure-induced structural evolution has been correlated with the vibrational modes corresponding to the Cu-O bonds. A strong negative pressure dependence of hydroxyl mode frequencies (as observed from the mid-IR absorption spectra) supports the pressure-induced structural disordering at higher pressures.

Manifestation of long-range ordered state in layered VX2 (X = Cl, Br, I) systems

We report the first-principles based density functional investigation of correlated magnetic behavior for the layered VX2 (X = Cl, Br, I) system both in bulk and monolayer forms. The bulk system stabilizes in the Néel 120° spin structure with the onset of long-range order at a very low temperature. However, a monolayer of the same system results in a two-dimensional long-range ordered spin-gel configuration in the a-b plane. The occurrence of this two-dimensional non-collinear long-range order for such hexagonal systems with honeycomb topology may provide an additional feature for controlling the use of such materials in magnetic memory devices.

1D/2D Hybrid Te/Graphene and Te/MoS2: Multifaceted Broadband Photonics and Green-Energy Applications

We highlight the enhanced electronic and optical functionalization in the hybrid heterojunction of one-dimensional (1D) tellurene with a two-dimensional (2D) monolayer of graphene and MoS₂ in both lateral and vertical geometries. The structural configurations of these assemblies are optimized with a comparative analysis of the energetics for different positional placements of the 1D system with respect to the hexagonal 2D substrate. The 1D/2D coupling of the electronic structure in this unique assembly enables the realization of the three different types of heterojunctions, viz. type I, type II, and Z-scheme. The interaction with 1D tellurene enables the opening of a band gap of the order of hundreds of meV in 2D graphene for both lateral and vertical geometries. With both static and time-dependent first-principles analysis, we indicate their potential applications in broadband photodetection and absorption, covering a wide range of visible to infrared (near-IR to mid-IR) spectrum from 380 to 10 000 nm. We indicate that this 1D/2D assembly also has bright prospects in green-energy harvesting.

Spin interactions in mineral libethenite series: evolution of low-dimensional magnetism

Interesting magnetic properties and spin-exchange interactions along various possible pathways in the half-integral spin quantum magnetic tetramer system: A(2)PO(4)OH (A=Co, Cu) are investigated. Interplay of structural distortion and the magnetic properties with the evolution of localized band structure explain the gradual transition from a three-dimensional antiferromagnet to a low-dimensional frustrated magnetic system along the series. A detailed study of the exchange mechanism in this system explores various possibilities of complex magnetic interaction. The electronic structure of this series, studied with the help of different appropriate density functional approaches such as Nth order muffin-tin orbital (NMTO) and plane-wave pseudopotential calculations incorporating onsite Coulomb repulsion (U), identifies the underlying magnetic exchange mechanism of this series. Thereafter a generalized minimal model spin-Hamiltonian is constructed for the low-dimensional system. Solution of this model Hamiltonian within first-order perturbation theory results in the evaluation of spin-gap in the spin-tetramer system. In addition, the effects of size confinement and volume reduction on the relevant exchange integrals and spin-gap of the low-dimensional system are also discussed.

Evaluation of the efficacy of a combination of diltiazem and periprostatic nerve block in pain control during transrectal ultrasonography-guided biopsy of the prostate

INTRODUCTION

The choice of analgesia during prostate biopsy remains controversial. The pain has dual origin: from the insertion of the probe as well as the biopsy itself. Periprostatic nerve block (PPNB) is currently the gold standard modality for decreasing pain of prostate biopsy but it does not alleviate the pain of probe insertion. A randomised controlled trial was performed to test the efficacy and safety of the combination of topical application of diltiazem gel and PPNB for pain control during transrectal ultrasonography guided prostate biopsy.

METHODS

A total of 73 patients who were to undergo their first prostate biopsy were randomised to receive either 2ml of 2% topical diltiazem gel or a placebo 15 minutes before the biopsy. All the patients then had a PPNB using 1% lignocaine. A ten- point visual analogue scale was used to record the pain immediately after the insertion of the probe and during the biopsy. Any adverse effects were also recorded.

RESULTS

There was no significant difference in the mean age and prostate volumes between the groups. There was a significantly lower mean pain score due to probe insertion in those patients who received topical diltiazem than in the placebo group (p<0.0001). There was no significant difference between the pain scores during the biopsy itself between the two groups.

CONCLUSIONS

Topical diltiazem significantly reduces the pain of probe insertion during prostate biopsy and can be used effectively as an adjuvant to PPNB.

Electrically Controlled Excitons, Charge Transfer Induced Trions, and Narrowband Emitters in MoSe2-WSe2 Lateral Heterostructure

Controlling excitons and their transport in two-dimensional (2D) transition metal dichalcogenide heterostructures is central to advancing photonics and electronics on-chip integration. We investigate the controlled generation and manipulation of excitons and their complexes in monolayer MoSe2-WSe2 lateral heterostructures (LHSs). Incorporating graphene as a back gate and edge contact in a field-effect transistor geometry, we achieve the precise electrical tuning of exciton complexes and their transfer across interfaces. Photoluminescence and photocurrent maps at 4 K reveal the synergistic effect of the local electric field and interface phenomena in the modulation of excitons, trions, and free carriers. We observe spatial variations in the exciton and trion densities driven by exciton-trion conversion under electrical manipulation. Additionally, we demonstrate controlled narrow-band emissions within the LHS through carrier injection and electrical biasing. Density functional theory calculation reveals significant band modification at the lateral interfaces. This work advances exciton manipulation in LHS and shows promise for next-generation 2D quantum devices.

Correction to Stable Sulfuric Vapor Transport and Liquid-Sulfur Growth on Transition Metal Dichalcogenides

[This corrects the article DOI: 10.1021/acs.cgd.2c01318.].