Piezoresponse force microscopy for polarity imaging of GaN

The polarity distribution of GaN based lateral polarity heterostructures is investigated by piezoresponse force microscopy (PFM). Simultaneous imaging of surface morphology, as well as the phase and magnitude of the piezoelectric response, is performed by PFM on a GaN film with patterned polarities on a c-Al2O3 substrate. We demonstrate that the polarity distribution of GaN based lateral polarity heterostructures can be deduced from the phase image of the piezoresponse with nanometer scale spatial resolution

A Critical Analysis of Techniques and Basic Phenomena Related to Deposition of High Temperature Superconducting Thin Films

The processes involved in plasma and ion beam sputter-, electron evaporation-, and laser ablation-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. Research is now demonstrating that the introduction of oxygen into the growing film, simultaneously with the deposition of the film components, is necessary to produce as-deposited superconducting films at relatively low substrate temperatures

Domain Wall Enabled Hysteresis-Free Steep Slope Switching in MoS2_2 Transistors

The device concept of operating ferroelectric field effect transistors (FETs) in the negative capacitance (NC) regime offers a promising route for achieving energy-efficient logic applications that can outperform the conventional CMOS technology, while the viable mechanisms for stabilizing the NC mode remain a central topic of debate. In this work, we report hysteresis-free steep slope switching in few-layer and bilayer MoS$_2$ transistors back-gated by single layer polycrystalline PbZr$_{0.35}$Ti$_{0.65}$O$_3$ films. The devices exhibit current on/off ratios up to 8$\times$10$^6$ within an ultra-low gate voltage window of V$_g$ = $\pm$0.5 V and subthreshold swing as low as 9.7 mV/decade at room temperature, transcending the 60 mV/decade Boltzmann limit. Unlike previous studies, the quasi-static NC mode is realized in a ferroelectric without involving an additional dielectric layer. Theoretical modeling reveals the dominant role of the metastable polar states within ferroelectric domain walls in enabling the NC mode in the MoS$_2$ transistors. Our findings shed light into a new mechanism for NC operation, providing a simple yet effective material strategy for developing high speed, low-power 2D nanoelectronics.Comment: 15 pages, 5 figure

A review of basic phenomena and techniques for sputter-deposition of high temperature superconducting films

The processes involved in plasma and ion beam sputter-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Control of film composition is a major issue in sputter-deposition of multicomponent materials. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. It has been understood for some time that for Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} deposition, the most intensely studied high-{Tc} compound, incorporation of sufficient oxygen into the film during deposition is necessary to produce as-deposited superconducting films at relatively substrate temperatures. Recent results have shown that with the use of suitable buffer layers, high quality Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} sputtered films can be obtained on Si substrates without the need for post-deposition anneal processing. This review is mainly focussed on issues related to sputter-deposition of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin films, although representative results concerning the bismuth and thallium based compounds are included. 143 refs., 11 figs

Реакция фоторождения мезонов на нуклонах и ядрах в резонансной области энергий

Исследования реакции фоторождения мезонов на нуклонах необходимы для получения спектра возбужденных барионных резонансов. В данной работе исследуется кинематика реакции фоторождения на протоне каона и вычислены сечения в рамках изобарной модели этой реакции в области энергии возбуждения резонанса N(1900)3/2+ с помощью формулы Брейта-Вигнера для изолированного резонанса и мультипольного анализа. Полученные оценки сечения согласуются с имеющимися экспериментальными данными.Investigations of the photoproduction of mesons on nucleons are necessary for obtaining the spectrum of excited baryon resonances. In this paper, we study the kinematics of the photoproduction reaction on the proton of the kaon and calculate the cross sections in the framework of the isobar model of this reaction in the region of the excitation energy of resonance N (1900) 3/2 * using the Breit-Wigner formula for isolated resonance and multipole analysis. The obtained estimates of the cross section agree with the available experimental data

Lead zirconate titanate on base metal foils: An approach for embedded high-K passive components

An approach for embedding high-K dielectric thin films into polymer packages has been developed. Pb{sub 0.85}La{sub 0.15}(Zr{sub 0.52}Ti{sub 0.48}){sub 0.96}O{sub 3} thin films were prepared by chemical solution deposition on 50 {micro}m thick Ni-coated Cu foils. Sputter deposited Ni top electrodes completed the all base-metal capacitor stack. After high temperature N{sub 2} crystallization anneals, the PLZT composition showed reduction resistance while the base-metal foils remained flexible. Capacitance density and Loss tangent values range between 300 and 400 nF/cm{sup 2} and 0.01 and 0.02 from 1 to 1,000 kHz respectively. These properties represent a 2 to 3 order of magnitude improvement over available embedded capacitor technologies for polymeric packages

Measurement and calculation of PZT thin film longitudinal piezoelectric coefficients.

The ferroelectric and piezoelectric properties of 2000 {angstrom} thick chemical solution deposited Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films were investigated. Several Zr/Ti ratios were studied: 30/70, 50/50 and 65/35, which correspond to tetragonal, near-morphotropic, and rhombohedral symmetries. In all samples, a {l_brace}111{r_brace}-texture is predominant. Longitudinal piezoelectric coefficients and their dc field dependence were measured using the contact AFM method. The expected trend of a maximum piezoelectric coefficient at or near to the MPB was not observed. The composition dependence was small, with the maximum d{sub 33} occurring in the tetragonal material. To explain the results, crystallographic texture and film thickness effects are suggested. Using a modified phenomenological approach, derived electrostrictive coefficients, and experimental data, d{sub 33} values were calculated. Qualitative agreement was observed between the measured and calculated coefficients. Justifications of modifications to the calculations are discussed