Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D ß-Ga2O3.

Wide bandgap semiconductors such as gallium oxide (Ga2O3) have attracted much attention for their use in next-generation high-power electronics. Although single-crystal Ga2O3 substrates can be routinely grown from melt along various orientations, the influence of such orientations has been seldom reported. Further, making rectifying p-n diodes from Ga2O3 has been difficult due to lack of p-type doping. In this study, we fabricated and optimized 2D/3D vertical diodes on ß-Ga2O3 by varying the following three factors: substrate planar orientation, choice of 2D material and metal contacts. The quality of our devices was validated using high-temperature dependent measurements, atomic-force microscopy (AFM) techniques and technology computer-aided design (TCAD) simulations. Our findings suggest that 2D/3D ß-Ga2O3 vertical heterojunctions are optimized by substrate planar orientation (-201), combined with 2D WS2 exfoliated layers and Ti contacts, and show record rectification ratios (>106) concurrently with ON-Current density (>103 A cm-2) for application in power rectifiers.

Atomic transistors based on seamless lateral metal-semiconductor junctions with a sub-1-nm transfer length.

The edge-to-edge connected metal-semiconductor junction (MSJ) for two-dimensional (2D) transistors has the potential to reduce the contact length while improving the performance of the devices. However, typical 2D materials are thermally and chemically unstable, which impedes the reproducible achievement of high-quality edge contacts. Here we present a scalable synthetic strategy to fabricate low-resistance edge contacts to atomic transistors using a thermally stable 2D metal, PtTe2. The use of PtTe2 as an epitaxial template enables the lateral growth of monolayer MoS2 to achieve a PtTe2-MoS2 MSJ with the thinnest possible, seamless atomic interface. The synthesized lateral heterojunction enables the reduced dimensions of Schottky barriers and enhanced carrier injection compared to counterparts composed of a vertical 3D metal contact. Furthermore, facile position-selected growth of PtTe2-MoS2 MSJ arrays using conventional lithography can facilitate the design of device layouts with high processability, while providing low contact resistivity and ultrashort transfer length on wafer scales.

Impact of mentoring on socio-emotional and mental health outcomes of youth with learning disabilities and attention-deficit hyperactivity disorder.

BACKGROUND: Learning disabilities (LD) and attention-deficit hyperactivity disorder (ADHD) are often accompanied by significant socio-emotional impairments and mental health challenges. However, there is a lack of controlled, quantitative research on potential interventions to address this issue. The current study evaluated the impact of a near-peer mentoring program for youth with LD/ADHD designed to promote socio-emotional well-being. METHODS: Youth with LD/ADHD who participated in the mentoring program (Mentored; n=99) were compared to non-mentored youth with LD/ADHD (Control-NM; n=51) and typically-developing youth without LD/ADHD (Control-TD; n=81) pre-mentoring in the fall, and post-mentoring in the spring. Participants were assessed on self-report measures of anxiety, depression, interpersonal relations, and self-esteem. RESULTS: Youth with LD/ADHD showed significantly higher scores of depression and significantly lower scores of interpersonal relations compared to the Control-TD group at fall baseline. The depression and self-esteem scores of the Mentored group significantly decreased and increased respectively after mentoring. These changes were associated with mentee-perceived mentorship quality. The Control-NM group showed significant decreases in both self-esteem and interpersonal relations, as well as increases in depression over time, while the Control-TD group remained stable across all measures. CONCLUSIONS: Results suggest that mentoring shows promise as a potential intervention for youth with LD/ADHD and co-occurring socio-emotional and mental health difficulties. The study is the first, to our knowledge, to quantify the effect of a near-peer mentoring program on youth with LD/ADHD in a design with two control groups. Implications for research and practice involving LD, ADHD, and mental health disorders are discussed.