Ultralow Contact Resistance and Efficient Ohmic Contacts in MoGe₂P₄–Metal Contacts

The MoGe2P4 monolayer, an emerging semiconductor with high carrier mobility, can be proposed as a promising channel material in field effect transistors (FETs). The contact resistance between MoGe2P4 and the metal electrode will limit the performance of a realistic FET. Using density functional theory (DFT) calculations, we explore the contact properties of a MoGe2P4 monolayer with six bulk metal electrodes (In, Ag, Au, Cu, Pd, and Pt). It is demonstrated that the Ohmic contacts are formed in all MoGe2P4–metal contacts due to the strong interfacial interactions, suggesting the high carrier injection efficiency. In addition, the MoGe2P4–Cu, −Pd, and −Pt contacts present 100% tunneling probability due to the absence of the tunneling barrier width. The tunneling probabilities of the MGP–In, MGP–Ag, and MGP–Au contacts are exceptionally higher than those of most other 2D semiconductors. Moreover, the tunneling-specific resistivity of all MoGe2P4–metal contacts is relatively low, indicating an ultralow contact resistance and excellent performance. These findings provide a useful guideline to design high-performance MoGe2P4-based electronic devices

New Insights into Electrochemical Lithiation/Delithiation Mechanism of α‑MoO₃ Nanobelt by in Situ Transmission Electron Microscopy

The α-MoO₃ nanobelt has great potential for application as anode of lithium ion batteries (LIBs) because of its high capacity and unique one-dimensional layer structure. However, its fundmental electrochemical failure mechanism during first lithiation/delithiation process is still unclear. Here, we constructed an electrochemical setup within α-MoO₃ nanobelt anode inside a transmission electron microscope to observe in situ the mircostructure evolution during cycles. Upon first lithiation, the α-MoO₃ nanobelt converted into numerous Mo nanograins within the Li₂O matrix, with an obvious size expansion. Interestingly, α-MoO₃ nanobelt was found to undergo a two-stage delithiation process. Mo nanograins were first transformed into crystalline Li_1.66Mo_0.66O₂ along with the disappearance of Li₂O and size shrink, followed by the conversion to amorphous Li₂MoO₃. This irreversible phase conversion should be responsible for the large capacity loss in first cycle. In addition, a fully reversile phase conversion between crystalline Mo and amorphous Li₂MoO₃ was revealed accompanying the formation and disapperance of the Li₂O layer during the subsequent cycles. Our experiments provide direct evidence to deeply understand the distinctive electrochemical lithiation/delithiation behaviors of α-MoO₃ nanobelt, shedding light onto the development of α-MoO₃ anode for LIBs

Semiconductor to Metal to Half-Metal Transition in Pt-Embedded Zigzag Graphene Nanoribbons

The electronic and magnetic properties of Pt-embedded zigzag graphene nanoribbons (Pt–ZGNRs) are investigated using density-functional theory calculations. It is found that Pt–ZGNRs exhibit a semiconductor–metal–half-metal transition as the position of Pt substitutional impurities in the ribbon changes from the center to edge sites. This behavior can be attributed to the interaction between Pt impurities and edge states of ZGNRs, which governs the electron occupation of the edge states. The transition always occurs independent of ribbon width. However, Pt impurity concentration is important for obtaining this transition. Our results demonstrate that Pt–ZGNRs can be used as versatile electronic devices

Tunable Schottky Barrier and Efficient Ohmic Contacts in MSi₂N₄ (M = Mo, W)/2D Metal Contacts

Monolayer MSi2N4 (M = Mo, W) has been fabricated and proposed as a promising channel material for field-effect transistors (FETs) due to the high electron/hole mobility. However, the barrier between the metal electrode and MSi2N4 will affect device performance. Hence, it is desirable to reduce the barrier for achieving high-performance electrical devices. Here, using density functional theory (DFT) calculations, we systematically investigate the electrical properties of the van der Waals (vdW) contacts formed between MSi2N4 and two-dimensional (2D) metals (XY2, X = Nb, Ta, Y = S, Se, Te). It is found that the contact types and Schottky barrier height (SBH) of MSi2N4/XY2 can be effectively tuned by selecting 2D metals with different work functions (WFs). Specifically, n- and p-type Schottky contacts and Ohmic contacts can be achieved in MSi2N4/XY2. Among them, MoSi2N4/H-NbS2, WSi2N4/H-XS2, and WSi2N4/H-NbSe2 present Ohmic contacts due to the high WF of 2D metals. Notably, the pinning factors of MSi2N4/XY2 are obviously larger than those of the other 2D semiconductor/metal contacts, indicating that the Fermi-level pinning (FLP) effect is weak in MSi2N4/XY2. Therefore, vdW stack engineering can strongly weaken the FLP effect, making the Schottky barrier tunable in MSi2N4/XY2 by choosing 2D metals with different WFs. The results provide important insights into the selection of appropriate electrodes and valuable guidance for the development of MSi2N4-based 2D electronic devices with high performance

Table_1_LncmiRHG-MIR100HG: A new budding star in cancer.docx

MIR100HG, also known as lncRNA mir-100-let-7a-2-mir-125b-1 cluster host gene, is a new and critical regulator in cancers in recent years. MIR100HG is dysregulated in various cancers and plays an oncogenic or tumor-suppressive role, which participates in many tumor cell biology processes and cancer-related pathways. The errant expression of MIR100HG has inspired people to investigate the function of MIR100HG and its diagnostic and therapeutic potential in cancers. Many studies have indicated that dysregulated expression of MIR100HG is markedly correlated with poor prognosis and clinicopathological features. In this review, we will highlight the characteristics and introduce the role of MIR100HG in different cancers, and summarize the molecular mechanism, pathways, chemoresistance, and current research progress of MIR100HG in cancers. Furthermore, some open questions in this rapidly advancing field are proposed. These updates clarify our understanding of MIR100HG in cancers, which may pave the way for the application of MIR100HG-targeting approaches in future cancer diagnosis, prognosis, and therapy.</p

Solubility of Boron, Carbon, and Nitrogen in Transition Metals: Getting Insight into Trends from First-Principles Calculations

Efficient chemical vapor deposition synthesis of two-dimensional (2D) materials such as graphene, boron nitride, and mixed BCN systems with tunable band gaps requires precise knowledge of the solubility and mobility of B/C/N atoms in the transition metals (TMs) used as substrates for the growth. Yet, surprisingly little is known about these quantities either from experiments or simulations. Using first-principles calculations, we systematically study the behavior of B/C/N impurity atoms in a wide range of TMs. We compute formation energies of B/C/N interstitials and demonstrate that they exhibit a peculiar but common behavior for TMs in different rows of the periodic table, as experimentally observed for C. Our simulations indicate that this behavior originates from an interplay between the unit cell volume and filling of the d-shell electronic states of the metals. We further assess the vibrational and electronic entropic contributions to the solubility, as well as the role of anharmonic effects. Finally, we calculate the migration barriers, an important parameter in the growth kinetics. Our results not only unravel the fundamental behavior of interstitials in TMs but also provide a large body of reference data, which can be used for optimizing the growth of 2D BCN materials

Mapping the Space of Inorganic and Hybrid Halides and Their Optical Properties Using Mechanochemistry and First-Principles Calculations

Inorganic and hybrid metal halides (MHs) are a class of ionic compounds that attract growing interest due to their richness of structure, properties, and resulting applications. These are largely ionic in nature and hence dominantly follow solid-state synthesis reactions rather than the solution approach. Keeping the importance of these materials in mind, herein, combination reactions of compounds via mechanochemistry is considered as a universal synthetic approach for the synthesis of MHs, and a library of MHs, including all inorganic MHs, ternary (A–B–X) MHs, enormous number of quaternary MHs based on representative 10 double perovskites (A–B–B′–X), and most of the hybrid ones based on randomly selected 49 samples as representative from the 1300 ones, are reported. The fundamental structure–property relationships are well revealed, where most of the MHs exhibit bright photoluminescence and/or magnetic properties for a few materials. Hence, the adopted concept of material design and related with their crystal structure and material properties for such a large number of halide materials not only help in building a library but also provide fundamental guidance to develop new MH materials with selective optoelectronic and magnetic properties.

Electron Beam Etching of CaO Crystals Observed Atom by Atom

With the rapid development of nanoscale structuring technology, the precision in the etching reaches the sub-10 nm scale today. However, with the ongoing development of nanofabrication the etching mechanisms with atomic precision still have to be understood in detail and improved. Here we observe, atom by atom, how preferential facets form in CaO crystals that are etched by an electron beam in an in situ high-resolution transmission electron microscope (HRTEM). An etching mechanism under electron beam irradiation is observed that is surprisingly similar to chemical etching and results in the formation of nanofacets. The observations also explain the dynamics of surface roughening. Our findings show how electron beam etching technology can be developed to ultimately realize tailoring of the facets of various crystalline materials with atomic precision

Identification of Single Nucleotides by a Tiny Charged Solid-State Nanopore

Discrimination of single nucleotides by a nanopore remains a challenge because of the minor difference among the four types of single nucleotides. Here, the blockade currents induced by the translocation of single nucleotides through a 1.8 nm diameter silicon nitride nanopore have been measured. It is found that the single nucleotides are driven through the nanopore by an electroosmotic flow instead of electrophoretic force when a bias voltage is applied. The blockade currents for the four types of single nucleotides are unique and differentiable, following the order of the nucleotide volume. Also, the dwell time for each single nucleotide can last for several hundred microseconds with the advantage of the electroosmotic flow, which is helpful for single nucleotide identification. The dwell-time distributions are found to obey the first-passage time distribution from the 1D Fokker–Planck equation, from which the velocity and diffusion constant of each nucleotide can be deduced. Interestingly, the larger nucleotide is found to translocate faster than the smaller one inside the nanopore because the larger nucleotide has a larger surface area, which may produce larger drag force induced by the electroosmotic flow, which is validated by molecular dynamics simulations

Visualizing the Electrochemical Lithiation/Delithiation Behaviors of Black Phosphorus by <i>in Situ</i> Transmission Electron Microscopy

Black phosphorus (BP) has drawn growing attention as the anode material for lithium-ion batteries (LIBs) because of its high theoretical lithium storage capacity. However, its electrochemical processes and fundamental failure mechanisms have not been completely understood due to the lack of direct evidence. Here, we report the direct visualization of the electrochemical lithiation/delithiation behavior of the BP anode in nano-LIBs using the <i>in situ</i> transmission electron microscopy technique. Upon lithiation, the BP anode is found to undergo obvious anisotropic size expansion and phase change from orthorhombic BP to amorphous Li_<i>x</i>P_<i>y</i> compounds. Unexpectedly, the BP anode pulverizes suddenly during discharging, resulting in irreversibility of the lithiated product and thus poor electrochemical cycling performance. This finding discloses that the failure mechanism of the BP anode is mainly correlated with the delithiation process rather than the lithiation one, which subverts the commonly accepted understanding. The new mechanism insights would serve to provide viable solutions for eliminating rapid capacity fading that plagues the bulk BP LIBs