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<jats:title>Abstract</jats:title> <jats:p>Pd/Co<jats:sub>2</jats:sub>MnSi (CMS)/NiFe<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> (NFO)/Pd multilayers were fabricated on F-mica substrate by magnetron sputtering. The best PMA performance of the multilayer structure Pd(3 nm)/CMS(5 nm)/NFO(0.8 nm)/Pd(3 nm) was obtained by adjusting the thickness of the CMS and NFO layers. F-mica substrate has a flatter surface than glass and Si/SiO<jats:sub>2</jats:sub> substrate. The magnetic anisotropy energy density (<jats:italic>K</jats:italic> <jats:sub>eff</jats:sub>) of the sample deposited on F-mica substrates is 0.6711 Merg/cm<jats:sup>3</jats:sup> (1 erg=10<jats:sup>−7</jats:sup> J), which is about 30% higher than that of the multilayer films deposited on glass (0.475 Merg/cm<jats:sup>3</jats:sup>) and Si/SiO<jats:sub>2</jats:sub> (0.511 Merg/cm<jats:sup>3</jats:sup>) substrates, and the <jats:italic>R</jats:italic> <jats:sub>Hall</jats:sub> and <jats:italic>H</jats:italic> <jats:sub>C</jats:sub> are also significantly increased. In this study, the NFO layer prepared by sputtering in the high purity Ar environment was exposed to the high purity O<jats:sub>2</jats:sub> atmosphere for 5 min, which can effectively eliminate the oxygen loss and oxygen vacancy in NFO, ensuring enough Co–O orbital hybridization at the interface of CMS/NFO, and thus effectively improve the sample PMA.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Effective probing current-induced magnetization switching is highly required in the study of emerging spin–orbit torque (SOT) effect. However, the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process, or the non-electric approach of Kerr imaging technique. Here, we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field. In this case, the symmetry of MR is broken, resulting in a resistance difference for opposite magnetization orientations. Moreover, the feasibility of our method is widely evidenced in heavy metal/ferromagnet (Pt/Ni<jats:sub>20</jats:sub>Fe<jats:sub>80</jats:sub> and W/Co<jats:sub>20</jats:sub>Fe<jats:sub>60</jats:sub>B<jats:sub>20</jats:sub>) and the topological insulator/ferromagnet (Bi<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub>/Ni<jats:sub>20</jats:sub>Fe<jats:sub>80</jats:sub>). Our work simplifies the characterization process of the in-plane magnetization switching, which can promote the development of SOT-based devices.</jats:p>

<jats:p>We use the ferromagnetic resonance (FMR) method to study the properties of ferromagnetic thin film, in which external stress anisotropy, fourfold anisotropy and uniaxial anisotropy are considered. The analytical expressions of FMR frequency, linewidth and the imaginary part of magnetic susceptibility are obtained. Our results reveal that the FMR frequency and the imaginary part of magnetic susceptibility are distinctly enhanced, and the frequency linewidth or field linewidth are broadened due to a strong external stress anisotropy field. The hard-axis and easy-axis components of magnetization can be tuned significantly by controlling the intensity and direction of stress and the in-plane uniaxial anisotropy field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We investigate the influence of source and drain bias voltages (<jats:italic>V</jats:italic> <jats:sub>DS</jats:sub>) on the quantum sub-band transport spectrum in the 10-nm width N-typed junctionless nanowire transistor at the low temperature of 6 K. We demonstrate that the transverse electric field introduced from <jats:italic>V</jats:italic> <jats:sub>DS</jats:sub> has a minor influence on the threshold voltage of the device. The transverse electric field plays the role of amplifying the gate restriction effect of the channel. The one-dimensional (1D)-band dominated transport is demonstrated to be modulated by <jats:italic>V</jats:italic> <jats:sub>DS</jats:sub> in the saturation region and the linear region, with the sub-band energy levels in the channel (<jats:italic>E</jats:italic> <jats:sub>channel</jats:sub>) intersecting with Fermi levels of the source (<jats:italic>E</jats:italic> <jats:sub>fS</jats:sub>) and the drain (<jats:italic>E</jats:italic> <jats:sub>fD</jats:sub>) in turn as <jats:italic>V</jats:italic> <jats:sub>g</jats:sub> increases. The turning points from the linear region to the saturation region shift to higher gate voltages with <jats:italic>V</jats:italic> <jats:sub>DS</jats:sub> increase because the higher Fermi energy levels of the channel required to meet the situation of <jats:italic>E</jats:italic> <jats:sub>fD</jats:sub> = <jats:italic>E</jats:italic> <jats:sub>channel</jats:sub>. We also find that the bias electric field has the effect to accelerate the thermally activated electrons in the channel, equivalent to the effect of thermal temperature on the increase of electron energy. Our work provides a detailed description of the bias-modulated quantum electronic properties, which will give a more comprehensive understanding of transport behavior in nanoscale devices.</jats:p>

<jats:p>Temperature-dependent and driving current-dependent electroluminescence spectra of two different InGaN/GaN multiple quantum well structures SA and SB are investigated, with the In composition in each well layer (WL) along the growth direction progressively increasing for SA and progressively decreasing for SB. The results show that SB exhibits an improved efficiency droop compared with SA. This phenomenon can be explained as follows: owing to the difference in growth pattern of the WL between these two samples, the terminal region of the WL in SB contains fewer In atoms than in SA, and therefore the former undergoes less In volatilization than the latter during the waiting period required for warming-up due to the difference in the growth temperature between well and barrier layers. This results in SB having a deeper triangular-shaped potential well in its WL than SA, which strongly confines the carriers to the initial region of the WL to prevent them from leaking to the p-GaN side, thus improving the efficiency droop. Moreover, the improvement in the efficiency droop for SB is also partly attributed to its stronger Coulomb screening effect and carrier localization effect.</jats:p>

<jats:p>Emissions by magnetic polarons and spin-coupled d–d transitions in diluted magnetic semiconductors (DMSs) have become a popular research field due to their unusual optical behaviors. In this work, high-quality NiI2(II)-doped CdS nanobelts are synthesized via chemical vapor deposition (CVD), and then characterized by scanning electron microscopy (SEM), x-ray diffraction, x-ray photoelectron spectroscopy (XPS), and Raman scattering. At low temperatures, the photoluminescence (PL) spectra of the Ni-doped nanobelts demonstrate three peaks near the band edge: the free exciton (FX) peak, the exciton magnetic polaron (EMP) peak out of ferromagnetically coupled spins coupled with FXs, and a small higher-energy peak from the interaction of antiferromagnetic coupled Ni pairs and FXs, called antiferromagnetic magnetic polarons (AMPs). With a higher Ni doping concentration, in addition to the d–d transitions of single Ni ions at 620 nm and 760 nm, two other PL peaks appear at 530 nm and 685 nm, attributed to another EMP emission and the d–d transitions of the antiferromagnetic coupled Ni<jats:sup>2+</jats:sup>–Ni<jats:sup>2+</jats:sup> pair, respectively. Furthermore, single-mode lasing at the first EMP is excited by a femtosecond laser pulse, proving a coherent bosonic lasing of the EMP condensate out of complicated states. These results show that the coupled spins play an important role in forming magnetic polaron and implementing related optical responses.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Light emission by inelastic tunneling (<jats:bold>LEIT</jats:bold>) from a metal–insulator–metal tunnel junction is an ultrafast emission process. It is a promising platform for ultrafast transduction from electrical signal to optical signal on integrated circuits. However, existing procedures of fabricating <jats:bold>LEIT</jats:bold> devices usually involve both top-down and bottom-up techniques, which reduces its compatibility with the modern microfabrication streamline and limits its potential applications in industrial scale-up. Here in this work, we lift these restrictions by using a multilayer insulator grown by atomic layer deposition as the tunnel barrier. For the first time, we fabricate an <jats:bold>LEIT</jats:bold> device fully by microfabrication techniques and show a stable performance under ambient conditions. Uniform electroluminescence is observed over the entire active region, with the emission spectrum shaped by metallic grating plasmons. The introduction of a multilayer insulator into the <jats:bold>LEIT</jats:bold> can provide an additional degree of freedom for engineering the energy band landscape of the tunnel barrier. The presented scheme of preparing a stable ultrathin tunnel barrier may also find some applications in a wide range of integrated optoelectronic devices.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A narrow linewidth Faraday anomalous dispersion optical filter (FADOF) with reflection configuration is achieved for the first time based on the cesium (Cs) ground state 6S<jats:sub>1/2</jats:sub> to the excited state 6P<jats:sub>3/2</jats:sub> transition at 852 nm. Compared with the conventional FADOF with transmission configuration, reflection-type FADOF can greatly improve the transmittance of optical filter under the same experimental parameters, because it allows signal light to go and return through the atomic vapor cell. In our experiment, peak transmittance at Cs 6S<jats:sub>1/2</jats:sub> <jats:italic>F</jats:italic> = 4–6P<jats:sub>3/2</jats:sub> transition is 81% for the reflection-type FADOF, and while 54% for the transmission-type FADOF when the temperature of Cs vapor cell and the axial magnetic field are 60 °C and 19 G. The idea of this reflection-type FADOF design has the potential to be applied to the FADOF operating between two excited states to obtain higher transmittance.</jats:p>

<jats:p>Atomic layer etching (ALE) of thin film GaN (0001) is reported in detail using sequential surface modification by BCl<jats:sub>3</jats:sub> adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a reactive ion etching system. The estimated etching rate of GaN is ∼ 0.74 nm/cycle. The GaN is removed from the surface of AlGaN after 135 cycles. To study the mechanism of the etching, the detailed characterization and analyses are carried out, including scanning electron microscope (SEM), x-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM). It is found that in the presence of GaCl<jats:sub> <jats:italic>x</jats:italic> </jats:sub> after surface modification by BCl<jats:sub>3</jats:sub>, the GaCl<jats:sub> <jats:italic>x</jats:italic> </jats:sub> disappears after having exposed to low energy Ar plasma, which effectively exhibits the mechanism of atomic layer etch. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.</jats:p>

<jats:p>A systematic investigation on PA-MBE grown GaN with low growth rates (less than 0.2 µm/h) has been conducted in a wide growth temperature range, in order to guide future growth of sophisticated fine structures for quantum device applications. Similar to usual growths with higher growth rates, three growth regions have been revealed, namely, Ga droplets, slightly Ga-rich and N-rich 3D growth regions. The slightly Ga-rich region is preferred, in which GaN epilayers demonstrate optimal crystalline quality, which has been demonstrated by streaky RHEED patterns, atomic smooth surface morphology, and very low defect related yellow and blue luminescence bands. The growth temperature is a critical parameter to obtain high quality materials and the optimal growth temperature window (~ 700–760 °C) has been identified. The growth rate shows a strong dependence on growth temperatures in the optimal temperature window, and attention must be paid when growing fine structures at a low growth rate. Mg and Si doped GaN were also studied, and both p- and n-type materials were obtained.</jats:p>