Search for: All records

In this work, we report on the anisotropic etching characteristics of β-Ga2O3 using triethylgallium (TEGa) performed in situ within an MOCVD chamber. At sufficiently high substrate temperatures, TEGa can act as a strong etchant for β-Ga2O3 utilizing the suboxide reaction between Ga and Ga2O3 [4 Ga(s) + Ga2O3 (s) → 3Ga2O (g)]. We observe that due to the monoclinic crystal structure of β-Ga2O3, TEGa etching on both (010) and (001) substrates is highly anisotropic in nature, in terms of both sidewall roughness and lateral etch rate. Smooth sidewalls are only obtained along crystal orientations that minimize sidewall surface energy. Utilizing this technique, we also demonstrate deep sub-micrometer fins with smooth sidewalls and high aspect ratios. Furthermore, we also demonstrate the damage-free nature of TEGa etching by fabricating Schottky diodes on the etched surface, which display no change in the net donor concentration. 

Abstract We report on a measurement of elastic electron scattering on argon performed with a novel cryogenic gas-jet target at the Mainz Microtron accelerator MAMI. The luminosity is estimated with the thermodynamical parameters of the target and by comparison to a calculation in distorted-wave Born approximation. The cross section, measured at new momentum transfers of 1.24 $$\hbox {fm}^{-1}$$ ${\text{fm}}^{-1}$and 1.55 $$\hbox {fm}^{-1}$$ ${\text{fm}}^{-1}$is in agreement with previous experiments performed with a traditional high-pressure gas target, as well as with modernab-initiocalculations employing state-of-the-art nuclear forces from chiral effective field theory. The nearly background-free measurement highlights the optimal properties of the gas-jet target for elements heavier than hydrogen, enabling new applications in hadron and nuclear physics. 

We report on the first deployment of a ytterbium (Yb) transportable optical lattice clock (TOLC), commercially shipping the clock 3000 km from Boulder, Colorado, to Washington DC. The system, composed of a rigidly mounted optical reference cavity, an atomic physics package, and an optical frequency comb, fully realizes an independent frequency standard for comparisons in the optical and microwave domains. The shipped Yb TOLC was fully operational within 2 days of arrival, enabling frequency comparison with a rubidium (Rb) fountain at the United States Naval Observatory (USNO). To the best of our knowledge, this represents the first deployment of a fully independent TOLC, including the frequency comb, coherently uniting the optical stability of the Yb TOLC to the microwave output of the Rb fountain. 

Multi-instance learning (MIL) handles data that is organized into sets of instances known as bags. Traditionally, MIL is used in the supervised-learning setting for classifying bags which contain any number of instances. However, many traditional MIL algorithms do not scale efficiently to large datasets. In this paper, we present a novel primal–dual multi-instance support vector machine that can operate efficiently on large-scale data. Our method relies on an algorithm derived using a multi-block variation of the alternating direction method of multipliers. The approach presented in this work is able to scale to large-scale data since it avoids iteratively solving quadratic programming problems which are broadly used to optimize MIL algorithms based on SVMs. In addition, we improve our derivation to include an additional optimization designed to avoid solving a least-squares problem in our algorithm, which increases the utility of our approach to handle a large number of features as well as bags. Finally, we derive a kernel extension of our approach to learn nonlinear decision boundaries for enhanced classification capabilities. We apply our approach to both synthetic and real-world multi-instance datasets to illustrate the scalability, promising predictive performance, and interpretability of our proposed method.