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<jats:p>We investigated the influence of an inserted bar on the hopper flow experimentally. Three geometrical parameters, size of upper outlet <jats:italic>D</jats:italic> <jats:sub>1</jats:sub>, size of lower outlet <jats:italic>D</jats:italic> <jats:sub>0</jats:sub>, and the height of bar <jats:italic>H</jats:italic>, are variables here. With varying <jats:italic>H</jats:italic> we found three regimes: one transition from clogging to a surface flow and another transition from a surface flow to a dense flow. For the dense flow, the flow rate follows Beverloo’s law and there is a saturation of inclination of free surface <jats:italic>θ</jats:italic>. We plotted the velocity field and there is a uniform linear relation between the particle velocity and depth from the free surface. We also found that the required value of <jats:italic>D</jats:italic> <jats:sub>1</jats:sub> to guarantee the connectivity of flow is little smaller than <jats:italic>D</jats:italic> <jats:sub>0</jats:sub>. For the transition from a surface flow to a dense flow, there is a jump of flow rate and the minimum <jats:italic>θ</jats:italic> for flowing is two degrees larger than the repose angle.</jats:p>

<jats:p>Study of two-dimensional (2D) magnetic materials is important for both fundamental research and application. Here we report molecular beam epitaxy growth of iodides, candidates for exhibiting 2D magnetism. Decomposition of CrI<jats:sub>3</jats:sub> is utilized to produce stable gaseous I<jats:sub>2</jats:sub> flux. Growth of MnI<jats:sub>2</jats:sub>, GdI<jats:sub>3</jats:sub>, and CrI<jats:sub>2</jats:sub> down to monolayer is successful achieved by co-depositing I<jats:sub>2</jats:sub> and corresponding metal atoms. The thin films of the three materials are characterized by scanning tunneling microscope and found to be insulators with bandgaps of 4.4 eV, 0.6 eV, and 3.0 eV, respectively. The film growth paves the way for further study of magnetic properties at the 2D limit.</jats:p>

<jats:p>Heat transfer is the foundation of freezing colloidal suspensions and a key factor for the interface movement. However, how the thermal conductivity of particles affects freezing microstructural evolution remains unknown. Here in this work, a mathematical model is built up to investigate thermal interactions among a growing particle layer, pulling speeds, and the freezing interface under a thermal gradient. Experiments are conducted to confirm the tendency predictions of the model. With the increase of pulling speeds, the drifting distance of the freezing interface increases and the time to finish drifting decreases. When the thermal conductivity of particles (<jats:italic>k</jats:italic> <jats:sub>p</jats:sub>) is smaller than that of the surrounding (<jats:italic>k</jats:italic> <jats:sub>w</jats:sub>), the freezing interface tends to go forward to the warm side. Contrarily, the freezing interface tends to go back to the cold side when the thermal conductivity of particles is larger than that of the surrounding (<jats:italic>α</jats:italic> = <jats:italic>k</jats:italic> <jats:sub>p</jats:sub>/<jats:italic>k</jats:italic> <jats:sub>w</jats:sub> &gt; 1). It originates from the shape of the local freezing interface: convex (<jats:italic>α</jats:italic> &lt; 1) or concave (<jats:italic>α</jats:italic> &gt; 1). These morphological changes in the local interface modify the premelting drag force <jats:italic>F</jats:italic> <jats:sub>f</jats:sub>. When <jats:italic>α</jats:italic> &lt; 1, <jats:italic>F</jats:italic> <jats:sub>f</jats:sub> decreases and the freezing morphology tends to be the frozen fringe. When <jats:italic>α</jats:italic> &gt; 1, <jats:italic>F</jats:italic> <jats:sub>f</jats:sub> increases and the freezing morphologies tend to be ice spears. These understandings of how the thermal conductivity of particles affect microstructural evolution may optimize the production of freeze-casting materials and their structural-functional properties.</jats:p>

<jats:p>We present a method of constructing composites composed of conjugated polyelectrolytes (CPEs) and single-walled carbon nanotubes (SWCNTs) to obtain a high-performing flexible thermoelectric generator. In this approach, three kinds of polymers, namely, poly[(1,4-(2,5-didodecyloxybenzene)-alt-2,5-thiophene] (P1), poly[(1,4-(2,5-bis-sodium butoxysulfonate-phenylene)-alt-2,5-thiophene] (P2), and poly[(1,4-(2,5-bis-acid butoxysulfonic-phenylene)-alt-2,5-thiophene] (P3) are designed, synthesized and complexed with SWCNTs as thermoelectric composites. The electrical conductivities of the CPEs/SWCNTs (P2/SWCNTs, and P3/SWCNTs) nanocomposites are much higher than those of non-CPEs/SWCNTs (P1/SWCNTs) nanocomposites. Among them, the electrical conductivity of P2/SWCNTs with a ratio of 1:4 reaches 3686 S⋅cm<jats:sup>−1</jats:sup>, which is 12.4 times that of P1/SWCNTs at the same SWCNT mass ratio. Moreover, CPEs/SWCNTs composites (P2/SWCNTs) display remarkably improved thermoelectric properties with the highest power factor (PF) of 163 μW⋅m<jats:sup>−1</jats:sup> ⋅ K<jats:sup>−2</jats:sup>. In addition, a thermoelectric generator is fabricated with P2/SWCNTs composite films, and the output power and power density of this generator reach 1.37 μW and 1.4 W⋅m<jats:sup>−2</jats:sup> (cross-section) at Δ <jats:italic>T</jats:italic> = 70 K. This result is over three times that of the thermoelectric generator composed of non-CPEs/SWCNTs composite films (P1/SWCNTs, 0.37 μW). The remarkably improved electrical conductivities and thermoelectric properties of the CPEs/SWCNTs composites (P2/SWCNTs) are attributed to the enhanced interaction. This method for constructing CPEs/SWCNTs composites can be applied to produce thermoelectric materials and devices.</jats:p>

<jats:p>During the preparation of the phase change memory, the deposition and chemical mechanical polishing (CMP) of titanium nitride (TiN) are indispensable. A new acidic slurry added with sodium hypochlorite (NaClO) as an oxidizer is developed for the CMP of TiN film. It has achieved a material removal rate of 76 nm/min, a high selectivity between TiN film and silica (SiO<jats:sub>2</jats:sub>) films of 128:1, a selectivity between TiN film and tungsten film of 84:1 and a high surface quality. To understand the mechanism of TiN CMP process, x-ray photoelectron (XPS) spectroscope and potentiodynamic polarization measurement are performed. It is found that the mechanism of TiN CMP process is cyclic reaction polishing mechanism. In addition, both static corrosion rate and the inductively coupled plasma results indicate TiN would not be dissolved, which means that the mechanical removal process of oxide layer plays a decisive role in the material removal rate. Finally, the mechanism of TiN polishing process is given based on the analysis of surface potential and the description of blocking function.</jats:p>

<jats:p>A novel shorted anode lateral-insulated gate bipolar transistor (SA LIGBT) with snapback-free characteristic is proposed and investigated. The device features a controlled barrier <jats:italic>V</jats:italic> <jats:sub>barrier</jats:sub> and resistance <jats:italic>R</jats:italic> <jats:sub>SA</jats:sub> in anode, named CBR LIGBT. The electron barrier is formed by the P-float/N-buffer junction, while the anode resistance includes the polysilicon layer and N-float. At forward conduction stage, the <jats:italic>V</jats:italic> <jats:sub>barrier</jats:sub> and <jats:italic>R</jats:italic> <jats:sub>SA</jats:sub> can be increased by adjusting the doping of the P-float and polysilicon layer, respectively, which can suppress the unipolar mode to eliminate the snapback. At turn-off stage, the low-resistance extraction path (N-buffer/P-float/polysilicon layer/N-float) can quickly extract the electrons in the N-drift, which can effectively accelerate the turn-off speed of the device. The simulation results show that at the same <jats:italic>V</jats:italic> <jats:sub>on</jats:sub> of 1.3 V, the <jats:italic>E</jats:italic> <jats:sub>off</jats:sub> of the CBR LIGBT is reduced by 85%, 73%, and 59.6% compared with the SSA LIGBT, conventional LIGBT, and TSA LIGBT, respectively. Additionally, at the same <jats:italic>E</jats:italic> <jats:sub>off</jats:sub> of 1.5 mJ/cm<jats:sup>2</jats:sup>, the CBR LIGBT achieves the lowest <jats:italic>V</jats:italic> <jats:sub>on</jats:sub> of 1.1 V compared with the other LIGBTs.</jats:p>

<jats:p>An analytical model of the power metal–oxide–semiconductor field-effect transistor (MOSFET) with high permittivity insulator structure (HKMOS) with interface charge is established based on superposition and developed for optimization by charge compensation. In light of charge compensation, the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage (<jats:italic>BV</jats:italic>) and minimizing specific ON-resistance (<jats:italic>R</jats:italic> <jats:sub>on,sp</jats:sub>). From this optimization method, it is very efficient to obtain the design parameters to overcome the difficulty in implementing the <jats:italic>R</jats:italic> <jats:sub>on,sp</jats:sub>–<jats:italic>BV</jats:italic> trade-off for quick design. The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region, the extraction of the parameters is qualitatively and quantitatively optimized for trading off <jats:italic>BV</jats:italic> and <jats:italic>R</jats:italic> <jats:sub>on,sp</jats:sub> with JFET effect taken into account.</jats:p>

<jats:p>AlGaN/GaN high-electron-mobility transistors (HEMTs) with postpassivation plasma treatment are demonstrated and investigated for the first time. The results show that postpassivation plasma treatment can reduce the gate leakage and enhance the drain current. Comparing with the conventional devices, the gate leakage of AlGaN/GaN HEMTs with postpassivation plasma decreases greatly while the drain current increases. Capacitance–voltage measurement and frequency-dependent conductance method are used to study the surface and interface traps. The mechanism analysis indicates that the surface traps in the access region can be reduced by postpassivation plasma treatment and thus suppress the effect of virtual gate, which can explain the improvement of DC characteristics of devices. Moreover, the density and time constant of interface traps under the gate are extracted and analyzed.</jats:p>

<jats:p>This paper presents the development of lateral depletion-mode n-channel 4H-SiC junction field-effect transistors (LJFETs) using double-mesa process toward high-temperature integrated circuit (IC) applications. At room temperature, the fabricated LJFETs show a drain-to-source saturation current of 23.03 μA/μm, which corresponds to a current density of 7678 A/cm<jats:sup>2</jats:sup>. The gate-to-source parasitic resistance of 17.56 kΩ ⋅ μm is reduced to contribute only 13.49% of the on-resistance of 130.15 kΩ ⋅ μm, which helps to improve the transconductance up to 8.61 μS/μm. High temperature characteristics of LJFETs were performed from room temperature to 400 °C. At temperatures up to 400 °C in air, it is observed that the fabricated LJFETs still show normally-on operating characteristics. The drain-to-source saturation current, transconductance and intrinsic gain at 400 °C are 7.47 μA/μm, 2.35 μS/μm and 41.35, respectively. These results show significant improvement over state-of-the-art and make them attractive for high-temperature IC applications.</jats:p>

<jats:p>The <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> films are prepared on polished Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> (0001) substrates by pulsed laser deposition at different oxygen partial pressures. The influence of oxygen partial pressure on crystal structure, surface morphology, thickness, optical properties, and photoluminescence properties are studied by x-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), spectrophotometer, and spectrofluorometer. The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure, the full width at half maximum (FWHM) and grain size increase. With the increase of oxygen pressure, the thickness of the films first increases and then decreases. The room-temperature UV-visible (UV-Vis) absorption spectra show that the bandgap of the <jats:italic>β</jats:italic>-Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film increases from 4.76 eV to 4.91 eV as oxygen pressure decreasing. Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm (∼ 4.0 eV), 360 nm (∼ 3.44 eV), 445 nm (∼ 2.79 eV), and 467 nm (∼ 2.66 eV), respectively. In addition, the total photoluminescence intensity decreases with oxygen pressure increasing, and it is found that the two UV bands are related to self-trapped holes (STHs) at O1 sites and between two O2-s sites, respectively, and the two blue bands originate from <jats:inline-formula> <jats:tex-math> <?CDATA ${{\rm{V}}}_{{\rm{Ga}}}^{2-}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi mathvariant="normal">V</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">Ga</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> <mml:mo>−</mml:mo> </mml:mrow> </mml:msubsup> </mml:mrow> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_30_2_028505_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> at Ga1 tetrahedral sites. The photoluminescence mechanism of the films is also discussed. These results will lay a foundation for investigating the Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film-based electronic devices.</jats:p>