Lateral Junction Research Articles

Imaging Stacking-Dependent Surface Plasmon Polaritons in Trilayer Graphene

We report an infrared (IR) imaging study of trilayer graphene (TLG) with both ABA (Bernal) and ABC (rhombohedral) stacking orders using the scattering-type scanning near-field optical microscope (SSNOM). With the SSNOM operating in the mid-IR region, we map in real space the surface plasmon polaritons of ABA TLG and ABC TLG, which are tunable with electrical gating. Through quantitative modeling of plasmonic imaging data, we find that the plasmon wavelength of ABA TLG is significantly larger than that of ABC TLG, resulting in a sizable impedance mismatch and hence a strong plasmon reflection at the ABA/ABC lateral junction. Further analysis indicates that the different plasmonic responses of the two types of TLG are directly linked to their distinct electronic structures and carrier properties. Our work uncovers the physics behind the stacking-dependent plasmonic responses of TLG and sheds light on future applications of TLG and the ABA/ABC junctions in IR plasmonics and planar nano-optics.

Selective Electron Beam Patterning of Oxygen-Doped WSe2 for Seamless Lateral Junction Transistors.

Surface charge transfer doping (SCTD) using oxygen plasma to form a p‐type dopant oxide layer on transition metal dichalcogenide (TMDs) is a promising doping technique for 2D TMDs field‐effect transistors (FETs). However, patternability of SCTD is a key challenge to effectively switch FETs. Herein, a simple method to selectively pattern degenerately p‐type (p+)‐doped WSe2 FETs via electron beam (e‐beam) irradiation is reported. The effect of the selective e‐beam irradiation is confirmed by the gate‐tunable optical responses of seamless lateral p+–p diodes. The OFF state of the devices by inducing trapped charges via selective e‐beam irradiation onto a desired channel area in p+‐doped WSe2, which is in sharp contrast to globally p+‐doped WSe2 FETs, is realized. Selective e‐beam irradiation of the PMMA‐passivated p+‐WSe2 enables accurate control of the threshold voltage (V th) of WSe2 devices by varying the pattern size and e‐beam dose, while preserving the low contact resistance. By utilizing hBN as the gate dielectric, high‐performance WSe2 p‐FETs with a saturation current of −280 µA µm−1 and on/off ratio of 109 are achieved. This study's technique demonstrates a facile approach to obtain high‐performance TMD p‐FETs by e‐beam irradiation, enabling efficient switching and patternability toward various junction devices.

Two-dimensional polarization doping of GaN heterojunction and its potential for realizing lateral p–n junction devices

In the gallium nitride (GaN) commercial applications such as high-power illumination and portable charging station, bipolar devices are highly demanded because of their superior power transfer capability. Also, in other scenarios of the monolithic integration where high electron mobility transistors (HEMTs) or superlattice-based devices are presented, the peripheral components are preferred to be lateral. However, to realize such a lateral bipolar junction in GaN, high-concentration p-type dopant doping is still challenging and hardly compatible with the HEMT integration. In this work, we proposed a novel strategy to form lateral bipolar GaN p–n junctions, enabled by the two-dimensional polarization doping. The theory and the simulation reveal this strategy features inspiring forwarding, blocking, and switching performance. Given the recent success of the GaN selective area regrowth techniques, the proposed lateral bipolar junction is highly promising in monolithic heterojunction integration in the future.

Atomic-Scale Insights into the Lateral and Vertical Epitaxial Growth in Two-Dimensional Pd2Se3-MoS2 Heterostructures.

Two-dimensional (2D) materials form heterostructures in both the lateral and vertical directions when two different materials are interfaced, but with totally different bonding mechanisms of covalent in-plane to van der Waal's layered interactions. Understanding how the competition between lateral and vertical forces influences the epitaxial growth is important for future materials development of complex mixed layered heterostructures. Here, we use atomic-resolution annular dark-field scanning transmission electron microscopy to study the detailed atomic arrangements at mixed 2D heterostructure interfaces composed of two semiconductors with distinctly different crystal symmetry and elemental composition, Pd2Se3:MoS2, in order to understand the role of different chemical bonds on the resultant epitaxy. Pd2Se3 is grown off the step edge in bilayer MoS2, and the vertical and lateral epitaxial relationships of the Pd2Se3-MoS2 heterostructures are investigated. We find that the similarity of geometry at the interface with one metal (Pd or Mo) atoms bonded with two chalcogens (S or Se) are the crucial factors to make the atomically stitched lateral junction of 2D heterostructures. In addition, the vertical van der Waal interactions that are normally dominant in layered materials can be overcome by in-plane forces if the interfacial atomic stitching is high in quality and low in defect density. This knowledge should help guide the approaches for improving the epitaxy in mixed 2D heterostructures and seamless stitching of in-plane 2D heterostructures with various complex monolayer structures.

Nanoarchitecture and molecular interactions of epithelial cell junction proteins revealed by super-resolution microscopy.

Epithelial cells are polarized with defined apical tight junctions (TJs), lateral adherens junctions (AJs), and basal integrin-matrix interactions. However, it is increasingly recognized that resident cell junction proteins can be found in varying locations and with previously unrecognized functions. Our study here presents the nanoarchitecture and nanocolocalization of cell junction proteins in culture and tissue by stochastic optical reconstruction microscopy (STORM). The Z-axial view of noncancerous MDCK-II and PZ-HPV-7 cell-cell junctions resolved β-catenin and p120ctn localizations to TJs and AJs, with p120ctn apical to β-catenin and colocalizing with TJ protein claudin-7. More basally, p120ctn and β-catenin become colocalized. This topography was lost in isogenic Ras-transformed MDCK cells and cancerous PC3 cells, where p120ctn becomes basally localized in relation to β-catenin. Claudin-7 gene conditional knockout (cKO) in mice also have altered polarity of p120ctn relative to β-catenin, like that seen in normal-to-cancer cell phenotypic transformation. Additionally, claudin-7 cKO resulted in redistribution and relocalization of other cell junction proteins, including claudin-1, zonula occludens-1, integrin α2, epithelial cell adhesion molecule, and focal adhesion kinase (FAK); specifically, integrin α2 and FAK were observed at the apical-lateral compartment. Our data show that STORM reveals regional cellular junction nanoarchitecture previously uncharacterized, providing new insight into potential trans-compartmental modulation of protein functions.

(Invited, Digital Presentation) Exploring Interfaces and Polarity to Realize Vertical III-Nitride Superjunction Devices

In recent years, there has been a surge of research and commercial interest in gallium nitride (GaN)-based devices for power conversion applications. This is largely motivated by the wide bandgap of GaN, which offers a unipolar limit of performance that is larger than that of silicon and silicon carbide. This performance ceiling, however, can be surpassed with the use of superjunction (SJ) structures, a strategy that has now been experimentally proven in both vertical Si- and SiC-based technologies. The ability to selectively dope lateral regions of a semiconductor is a requirement for SJ fabrication, with typical schemes relying on ion implantation, epitaxial regrowth or a combination of both. However, due to the challenges associated with applying conventional selective area doping techniques to GaN, vertical GaN SJ structures have remained elusive.Recently, our team proposed the use of lateral polar junctions (LPJs) to form vertical GaN SJ devices. This approach exploits the natural doping asymmetry between the N-polar and Ga-polar crystal orientations to simultaneously grow N-polar GaN for the n-type pillars and Ga-polar GaN for the p-type pillars. The first part of this talk will present a design framework for GaN SJ devices. This will reveal several critical design requirements: 1) doping in N-polar GaN must be reduced below 5 × 1017 cm-3 to achieve kV-class devices, 2) charge must be tightly balanced between neighboring pillars in the SJ structure to obtain efficient performance and 3) the barrier height to the N-polar GaN region must be tuned to suppress leakage currents and avoid bipolar operation.The next part of the talk will focus on the characterization of rectifying contacts to N-polar GaN. While the analysis of Schottky barrier diodes proved the ability to reduce doping to relevant levels, the low barrier height and enhanced chemical sensitivity of N-polar GaN make it challenging to process adequate devices. Thus, low-pressure chemical vapor deposited (LPCVD) silicon nitride (SiN) interlayers were introduced to increase the barrier height. This approach is enabled by surface-termination dependent barrier height and an amphoteric miniband for enhanced conduction via the interlayer. Moreover, the use of the LPCVD SiN interlayer enables operation of the diodes up to 400 °C compared to less than 200 °C for the reference case. In addition, N-polar GaN camel diodes were also designed, fabricated and tested to better tune the barrier height. The latter structure was incorporated into the first charge-balanced GaN superjunction device. A detailed electrical analysis of the GaN LPJ device will represent the final portion of this talk.The successful demonstration of these experimental building blocks paves the way for the GaN LPJ to be used in future high-voltage GaN SJ devices.

Air-Bridge Si Thermophotovoltaic Cell with High Photon Utilization

Thermophotovoltaic (TPV) cells convert photons emitted from hot surfaces into electrical power. Unlike solar cells, TPV cells can be placed in close proximity to the heat source, allowing below-bandgap (i.e., out-of-band, OOB) photons to be reflected and reabsorbed by the emitter. As the reflectance of OOB photons approaches unity, the spectral efficiency of the TPV becomes increasingly insensitive to the bandgap of the cell and the source temperature. Here, we employ air-bridge structures with a lateral junction Si TPV cell as a means of increasing OOB reflectivity, which allows for efficient operation at low thermal source temperatures that were long inaccessible to efficient Si TPV power generation. The devices exhibit an OOB reflectance of 98.0 ± 0.1% and an air-bridge scalability to at least 6 cm × 6 cm. Compared to devices with a Au back surface reflector (BSR), devices featuring an air-bridge BSR exhibit a 25% relative increase in power conversion efficiency at a thermal source temperature of 1988 K. Such performance improvements in TPV cells made with scalable and relatively low-cost Si can potentially expedite the widespread use of TPV systems in both energy storage and generation systems.

Low VπLπ and Driving Voltage Interleaved Silicon Phase Shifter for Modulation Applications

Interleaved doped Mach-Zehnder Modulators (MZMs) are one solution to attaining higher modulation efficiencies compared with lateral junction structures, due to greater modal overlap with the depletion regions of the PN junctions. In this work, we present an interleaved Si modulator device design and process simulation based on a three-step ion implantation process that aims to obtain a realistic PN junction doping profile using a Monte Carlo simulation method. A high doping concentration on the order of 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> for the P and N regions is explored. Device simulations to track the carrier motion under different voltage biases are performed. Using equivalent medium theory, we calculated the modulation efficiency V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> ·L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> of the interleaved Si modulator to be 0.19 V·cm under 1V reverse bias. This work is among the highest reported modulation efficiencies thus far in MZMs without photonic resonance structures.

Lateral magnetic tunnel junctions with a heterointerface‐induced half‐metallic electrode

The electronic properties of monolayer MnGeSe3 and MnGeSe3/CrI3 heterostructures were investigated by density functional theory (DFT) calculations. In the MnGeSe3/CrI3 heterostructure, the half-metal MnGeSe3 can induce the half-metallic properties of CrI3 by charge transfer. Based on the charge transfer effect, we designed lateral magnetic tunnel junctions (MTJs) in which MnGeSe3 attaches to the bottom of the detached CrI3 crystals. This model can form half-metallic-CrI3/insulating-CrI3/half-metallic-CrI3 MTJs, thereby avoiding the loss of half-metallic properties caused by defects and lattice distortion at the interface of traditional half-metallic MTJs. According to the extension length of the CrI3 layer, they can be divided into heteroelectrode MTJs and MnGeSe3-electrode MTJs. Half-metallic electrode MTJs are famous for their ultrahigh tunnel magnetoresistance (TMR), and the ability to maintain a stable TMR under bias has become the other significant target of half-metal MTJs. We find that the half-metallic gap of the electrode material can affect the threshold bias voltage in antiparallel configuration (APC) when opening and closing. The larger the half-metallic gap is, the larger the bias voltage required to generate the tunneling current, and correspondingly, the better its ability to maintain a high TMR. Therefore, it is imperative to find two-dimensional half-metallic materials with large half-metallic gaps. Our results provide a new idea for designing half-metallic electrode MTJs and provide a new understanding of the mechanism of half-metallic electrode MTJs under bias.

3-D Simulation Study of a Normally-OFF GaN Lateral Multi-Channel JFET With Optimized Electrical Field Transfer Terminal Structure

In this work, a lateral multichannel GaN-based junction field effect transistor (JFET) is proposed and studied by 3-D numerical simulation to realize normally- OFF operation and retain large output current simultaneously. Normally- OFF operation can be realized more easily due to the use of double side p-n junction gate for every single channel. We calculate the variations of the maximum saturation current and threshold voltage with channel thickness and doping concentration and obtain the corresponding transition chart from normally- ON to normally- OFF operation. Based on these optimized structure parameters, we further attempt electrical field transfer terminal technologies to improve the breakdown characteristics for the device, and we find that the drain field plate technology has much better effect than the reduced surface field technology, such that the drain field plate can transfer high electric field from the drain terminal into the insulation dielectric. The simulated breakdown voltage of the designed JFET with drain field plate reaches 880 V, leading to an increase by 50&#x0025; compared to that without drain field plate. In addition, the designed device shows a relatively high cutoff frequency up to gigahertz.

Dorsal Preservation Surgery: A Novel Modification for Dorsal Shaping and Hump Reduction.

A new technique for dorsal preservation rhinoplasty that minimizes recurrent hump deformity is introduced. The authors sought to present a novel dorsal roof flap (DRF) technique for modifying the nasal hump and dorsum while reducing morbidity. Twenty-two primary and 3 secondary rhinoplasty patients had 1 of 2 types of nasal DRF depending on hump composition. A triangular roof flap was created utilizing 2 incisions from W-point to lateral Keystone junction in cartilaginous humps (cartilaginous DRF) and to the nasion in osseocartilaginous humps (osseocartilaginous DRF). Then, septal strip excisions were conducted to lower the profile followed by nasal base narrowing. The DRF was then lowered to the desired profile line, any excess lateral wall height trimmed, and the DRF sutured to the upper lateral cartilages. Preoperative and postoperative nasolabial and nasoglabellar angles were measured on the photos. Mean follow-up was 10.3 (standard deviation, 4.41) months (range, 6-20 months). A total 22 humps were V-shape and 3 were S-shape. The composition of the hump was cartilaginous in 5 cases, bone in 7 cases, and combined in 13 cases. A cartilaginous DRF was utilized for the 5 cases with a cartilaginous hump and osseocartilaginous DRF was employed in the other 20 cases. There were no complications observed in the follow-up period and thus no revisions. The DRF technique allows preservation of the nasal dorsum and elimination of the dorsal hump while minimizing hump recurrence.

Longitudinal associations between social media use, mental well-being and structural brain development across adolescence

Youth of today grow up in a digital social world but the effects on well-being and brain development remain debated. This study tracked longitudinal associations between structural brain development, social media use and mental well-being.The study demonstrated two pathways of heterogeneity in brain development. First, adolescents who used social media more than their peers showed higher baseline cortical thickness in lateral prefrontal cortex (PFC) and medial PFC; and stronger decreases in the lateral PFC and temporal parietal junction. In contrast, adolescents with lower mental well-being showed lower baseline levels of surface area in the medial PFC and posterior superior temporal sulcus relative to their peers. Whereas the associations between structural brain development and well-being remained significant after correction for multiple testing, the results for social media use did not survive FDR correction.These findings demonstrate that although social media use and mental well-being were both associated with differential trajectories of brain development, the associations we report are distinct. These results show a nuanced perspective on the presumed relations between social media use and well-being and provide a starting point to further examine neural mechanisms that could explain which adolescents thrive by social media and which might be harmed.

Abstract P3-19-08: Breast cancer related lymphedema in patients undergoing RNI: Is the axillary lateral vessel thoracic junction an organ-at-risk?

Abstract Background: Breast-cancer related lymphedema (BCRL) is a devastating treatment complication driven by the extent of axillary surgery (axillary lymph node dissection [ALND] versus sentinel lymph node biopsy [SLNB]). Regional nodal irradiation (RNI) may increase the risk of BCRL by up to 5%. Recently, investigators identified a region of the axilla known as the axillary-lateral thoracic vessel juncture (ALTJ) as a potential organ-at-risk (OAR) demonstrating that increasing radiation dose to the ALTJ was associated with a higher risk of BCRL. Here, we set to validate whether radiation dose to the ALTJ is associated with BCRL. Materials/Methods: We identified patients with stage II-III breast cancer treated with adjuvant RNI after M or L from 2013-2018 excluding those with BCRL pre-radiation. RNI treatment planning included delineation of clinical target volumes (CTVs): breast or chest wall and regional lymph nodes per the RTOG Breast Cancer Atlas. The CTVs were expanded by 5mm to create the planning target volume (PTV). Dose delivered was 50 Gy/25 fractions with goal of 47.5 Gy (95%) to 95% of each PTV. We defined BCRL as difference in arm circumference between the ipsilateral and contralateral limb &amp;gt;2.5 cm at any 1 visit or ≥2 cm on at least 2 visits. All patients suspected of having BCRL at routine follow-up visits were evaluated by physical therapy. The ALTJ was retrospectively contoured and the following metrics collected: maximum/minimum/mean dose; V10Gy-V50Gy. Follow-up time was defined as the time from surgery to the development of BCRL or last follow-up. Cox proportional hazards regression models were used to test the association between clinical and dosimetric parameters with the development of BCRL. All variables with p&amp;lt;0.10 on univariate analysis were entered in the final multivariate model (p&amp;lt;0.05 considered statistically significant). Results: Population includes 378 patients with median age 53 years (interquartile range [IQR], 45-61 years), median body mass index (BMI) 28.4 kg/m2 (IQR, 24.3-33.4 kg/m2), 60% HR+/HER2-, 89% chemotherapy, 53% stage III, 71% underwent M, and 82% underwent ALND with median of 18 nodes removed (IQR, 11-25) and median of 2+ nodes (IQR, 1-5). Median follow-up time was 54.5 months (IQR, 40.3-72.2 months). The ALTJ and axilla PTV overlapped in 91% of the patients. BCRL developed in 97 patients (25.7%) at a median of 18.9 months (IQR, 9.9-30.6 months). The 4-year cumulative incidence of BCRL was 23.5% (26.6% ALND vs. 8.7% SLNB, p=0.002). On univariate analysis, increasing age (HR=1.02, p=.039), increasing BMI (HR=1.04, p=0.002), increasing number of nodes removed (HR=1.04, p&amp;lt;0.0001), and use of IMRT vs. 3DCRT (HR=1.50, p=0.041) were all significantly associated with developing BCRL while increasing size of the axilla PTV (HR=0.96, p=0.047) was associated with a lower risk. None of the ALTJ metrics were associated with developing BCRL. Increasing ALTJ V45 was marginally associated with a lower risk of BCRL (HR=0.96, p=0.091). On multivariate analysis, increasing age (HR=1.02, p=0.021), increasing BMI (HR=1.04, p=0.004), and increasing number of nodes removed (HR=1.03, p=0.001) were associated with a higher risk of developing BCRL while use of IMRT (HR=1.24, p=0.338), size of the axilla PTV (HR=0.96, p=0.110) and ALTJ V45 (HR=0.99, p=0.708) were not. There were 10 local-regional recurrence (LRR) events as a first failure, 8 of which occurred with simultaneous distant metastases (DM). Of these LRRs, 5 included an axillary nodal component (all with DM) resulting in a 2.6% 4-year LRR rate (1.4% axillary recurrence rate). Conclusion: In this analysis, ALTJ is not validated as a critical OAR for reducing BCRL risk. Until such an OAR is discovered, the axillary PTV should not be modified or dose reduced in efforts to reduce BCRL given the low LRR and inability to validate ALTJ as an OAR. Citation Format: Erin Healy, Sachin Jhawar, Sasha Beyer, Julia R White, Jose G Bazan. Breast cancer related lymphedema in patients undergoing RNI: Is the axillary lateral vessel thoracic junction an organ-at-risk? [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-19-08.

Strain-tunable in-plane ferroelectricity and lateral tunnel junction in monolayer group-IV monochalcogenides

2D ferroelectric materials are promising for designing low-dimensional memory devices. Here, we explore strain-tunable ferroelectric properties of group-IV monochalcogenides MX (M=Ge, Sn; X=S, Se) and their potential application in lateral field tunnel junction devices. We find that these monolayers have in-plane ferroelectricity, with their ferroelectric parameters being on par with other known 2D ferroelectric materials. Among SnSe, SnS, GeSe, and GeS, we find that GeS has the best ferroelectric parameters for device applications, which can be improved further by applying uniaxial tensile strain. We use the calculated ferroelectric properties of these materials to study the tunneling electroresistance (TER) of a 4 nm device based on a lateral ferroelectric tunnel junction. We find a substantial TER ratio of 103–105 in the devices based on these materials, which can be further improved up to a factor of 40 on the application of tensile strain.

Nanoscale Control of One-Dimensional Confined States in Strongly Correlated Homojunctions.

Construction of lateral junctions is essential to generate one-dimensional (1D) confined potentials that can effectively trap quasiparticles. A series of remarkable electronic phases in one dimension, such as Wigner crystallization, are expected to be realized in such junctions. Here, we demonstrate that we can precisely tune the 1D-confined potential with an in situ manipulation technique, thus providing a dynamic way to modify the correlated electronic states at the junctions. We confirm the existence of 1D-confined potential at the homojunction of two single-layer 1T-NbSe2 islands. Such potential is structurally sensitive and shows a nonmonotonic function of their interspacing. Moreover, there is a change of electronic properties from the correlated insulator to the generalized 1D Wigner crystallization while the confinement becomes strong. Our findings not only establish the capability to fabricate structures with dynamically tunable properties, but also pave the way toward more exotic correlated systems in low dimensions.

GaN lateral polar junction arrays with 3D control of doping by supersaturation modulated growth: A path toward III-nitride superjunctions

We demonstrate a pathway employing crystal polarity controlled asymmetric impurity incorporation in the wide bandgap nitride material system to enable 3D doping control during the crystal growth process. The pathway involves polarity specific supersaturation modulated growth of lateral polar structures of alternating Ga- and N-polar GaN domains. A STEM technique of integrated differential phase contrast is used to image the atomic structure of the different polar domains and their single atomic plane boundaries. As a demonstration, 1 μm wide alternating Ga- and N-polar GaN domains exhibiting charge balanced and periodic domains for superjunction technology were grown. The challenges in characterizing the resulting 3D doping profile were addressed with atom probe tomography with atomic scale compositional resolution corroborating capacitance measurements and secondary-ion mass spectroscopy analysis.

The Spin Transport Properties of Ni(111)/Snse/Ni(111) Lateral Tunnel Junction

The Spin Transport Properties of Ni(111)/Snse/Ni(111) Lateral Tunnel Junction

Characterization of Plasma Process-Induced Low-Density Defect Creation by Lateral Junction Leakage

In the design of ultralow leakage devices such as image sensors, it is necessary to understand the influence of low-density defects during plasma processing-plasma-induced physical damage (PPD)-on device performance. Defects created by plasma exposure act as carrier conduction sites and induce an increase in leakage (e.g., dark) current. This study proposes a PPD evaluation scheme for low-density defect assessments, specifically defects created in the lateral direction due to lateral stochastic straggling (lateral PPD). Two test structures were designed: a single device with a leakage current (Ileak) and a complementary metal-oxide-semiconductor image sensor (CIS) circuit with a dark current (Idark). The energy level and density of defects distributed in the lateral direction were estimated using the Shockley-Read-Hall (SRH) model. The energy level (Et) was derived using the SRH model from the temperature dependence of Ileak and Idark defined as the activation energy Ea. The trap density (Nt) was also determined. A comprehensive comparison of these parameters was conducted. Both Ileak and Idark are dependent on the contact opening diameter after plasma exposure, which implies the presence of defects in the lateral direction via lateral PPD. From the analysis of the temperature dependence of Ileak and Idark, the lateral PPD influenced the mean value of Ea. Moreover, we confirmed that an increase in Idark indicates an increase in the number of trap sites, and more specifically, an increase in defects at shallow levels. The derived trap site density in the CIS circuit was consistent with that of a single device. The proposed evaluation scheme is useful for PPD evaluation in the presence of low-density defects, and is critical for the design of future low-leakage devices.

Inter-facet junction effects on particulate photoelectrodes.

Particulate semiconductor photocatalysts are paramount for many solar energy conversion technologies. In anisotropically shaped photocatalyst particles, the different constituent facets may form inter-facet junctions at their adjoining edges, analogous to lateral two-dimensional (2D) heterojunctions or pseudo-2D junctions made of few-layer 2D materials. Using subfacet-level multimodal functional imaging, we uncover inter-facet junction effects on anisotropically shaped bismuth vanadate (BiVO4) particles and identify the characteristics of near-edge transition zones on the particle surface, which underpin the whole-particle photoelectrochemistry. We further show that chemical doping modulates the widths of such near-edge surface transition zones, consequently altering particles' performance. Decoupled facet-size scaling laws further translate inter-facet junction effects into quantitative particle-size engineering principles, revealing surprising multiphasic size dependences of whole-particle photoelectrode performance. The imaging tools, the analytical framework and the inter-facet junction concept pave new avenues towards understanding, predicting and engineering (opto)electronic and photoelectrochemical properties of faceted semiconducting materials, with broad implications in energy science and semiconductor technology.

3.48-nW 58.4ppm/°C Sub-threshold CMOS Voltage Reference with Four Transistors and Two Resistors

In this paper, an ultra-low power CMOS voltage reference capable of operating at sub-1[Formula: see text]V input supply is proposed. Four transistors biased in weak inversion are used to generate the required complementary-to-absolute-temperature (CTAT) and proportional-to-absolute-temperature (PTAT) voltages of the proposed circuit. Self-biasing of nature of the proposed configuration in the form of operational amplifier (opamp)-free ensure nano-power operation and eliminate the need for lateral bipolar junction transistors (BJTs) and offset cancelation techniques. A prototype of the circuit is designed and simulated in a standard 0.18-[Formula: see text]m CMOS process. Post-layout simulation results show that the circuit generates a reference voltage of 494[Formula: see text]mV with temperature coefficient (TC) of 58.4[Formula: see text]ppm/∘C across [Formula: see text]C to 85∘C; while the consuming power is lowered to 3.48[Formula: see text]nW at the minimum supply of 0.8[Formula: see text]V. The line sensitivity is 0.7%/V for the supply voltages from 0.8[Formula: see text]V to 1.8[Formula: see text]V, whereas the power supply ripple rejection (PSRR) is [Formula: see text]49.06[Formula: see text]dB at 1[Formula: see text]Hz. Monte Carlo simulation results of the voltage reference show a mean value of 497.2[Formula: see text]mV with [Formula: see text]/[Formula: see text] of 1.7%, demonstrating the robustness of the generated reference voltage against the process variations and mismatch.