Structural properties of Co2TiSi films on GaAs(001)
Co2TiSifilms weregrown by molecular beam epitaxy on GaAs(001) and analyzed using reflection high-energy electron diffraction, and electron microscopy. In addition,X-ray diffraction was combined withlattice parameter calculations bydensity functional theory comparing theL21 andB2 structures and considering the influence of non-stoichiometry. Columnargrowth is found and attributed to inhomogeneousepitaxial strain from non-random alloying. Infilms with thicknesses up to 13 nm, these columns may be the origin of perpendicular magnetization with the easy axis perpendicular to the sample surface. We foundL21 andB2 ordered reg...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: B. Jenichen, J. Herfort, M. Hanke, U. Jahn, X. Kong, M. T. Dau, A. Trampert, H. Kirmse and S. C. Erwin Source Type: research
Pressure and temperature dependence of the laser-induced plasma plume dynamics
The influence of different background gases and substrateheating on theplasma plumedynamics fromsilver ablation is investigated by species selected time and space resolvedimaging. The results provide a time-resolved understanding on how those process parameters affect theexpansion: from a freeexpansion in vacuum with velocities exceeding 20 000 m/s to a very slowexpansion in Ar at 1 × 10−1 mbar with arrival velocities of 280 m/s. In addition, we observe a rebound of the ablated material on the substrate holder leading to a re-coating of the ablated target. At 1 × 10−1 mbar, it seems that theexpansion o...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Alejandro Ojeda-G-P, Christof W. Schneider, Thomas Lippert and Alexander Wokaun Source Type: research
Optical and electronic properties of conductive ternary nitrides with rare- or alkaline-earth elements
Conductive nitrides, such as TiN, are key engineering materials for electronics, photonics, and plasmonics; one of the essential issues for such applications is the ability of tuning theconduction electron density, theresistivity, and theelectron scattering. While enhancing theconduction electron density and blueshifting the intraband absorption towards the UV were easily achieved previously, reducing theconduction electron density and redshifting the intraband absorption into the infrared are still an open issue. The latter is achieved in this work by alloying TiN by rare earth (RE = Sc, Y, La) or alkaline earth (AE...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: S. Kassavetis, A. Hodroj, C. Metaxa, S. Logothetidis, J. F. Pierson and P. Patsalas Source Type: research
Growth of Ni and Ni-Cr alloy thin films on MgO(001): Effect of alloy composition on surface morphology
The effects of substrate treatment,growth temperature, and composition on thesurface morphology of Ni-Crthin filmsgrown on MgO(001) are studied byscanning tunneling microscopy andatomic force microscopy. We demonstrate that a combination of acid-etched substrates and high temperature deposition (400 °C) will result in smooth films with well-defined terraces (up to 30 nm wide) that are suitable for the study of progression of chemical reactions on the surface. Two different treatments are used to prepare the MgO substrates for deposition and they introduce characteristic differences in fil msurface morphology.Thin fil...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Gopalakrishnan Ramalingam and Petra Reinke Source Type: research
Negative capacitance in optically sensitive metal-insulator-semiconductor-metal structures
We report a strong negativecapacitance effect in back to back combination of ametal-insulator-semiconductor(MIS)structure and a metal-semiconductor junction, which is fabricated on an n type Silicon-on-Insulator substrate. The MIS capacitor comprises a SiO2-HfO2insulator stack with embedded Pt nanoparticles. The capacitor undergoes a voltage stress process and thereby turns into a varactor and a photodetector. The negativecapacitance is observed only underillumination instructures that employ aSchottky back contact. A symmetric double or an asymmetric single negativecapacitance peak is observed depending on the nature ofil...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: V. Mikhelashvili, R. Padmanabhan, B. Meyler, S. Yofis and G. Eisenstein Source Type: research
The stress statistics of the first pop-in or discrete plastic event in crystal plasticity
The stress at which the first discrete plastic event occurs is investigated using extreme value statistics. It is found that the average of this critical stress is inversely related to thedeforming volume, via an exponentially truncated power-law. This is demonstrated for the first pop –in event observed in experimental nano-indentation data as a function of the indenter volume, and for the first discrete plastic event seen in adislocation dynamics simulation. When the underlying master distribution of critical stresses is assumed to be a power-law, it becomes possible to extract the density of discrete plastic events av...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: P. M. Derlet and R. Maa ß Source Type: research
Bragg superlattices formed in growing chemically vapor deposited diamond
A Braggsuperlattice is created in the process of thediamond growth from a gaseous phase via the nanoscaleboron modulationdoping method. To maximize the Braggsuperlatticereflection coefficient at the violet edge of the visible range, the thicknesses of either of two layers in its period were made close to the quarter-wavelength of radiation in this spectral domain. The vacuum wavelength dependence of the transition coefficient of electromagnetic radiation in the optical and near infrared range through thissuperlattice is measured. The most pronounced Bragg features are lying at the violet edge of the optical range, where th...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: V. A. Kukushkin, M. A. Lobaev, D. B. Radischev, S. A. Bogdanov, M. N. Drozdov, V. A. Isaev, A. L. Vikharev and A. M. Gorbachev Source Type: research
Systematic study on dynamic atomic layer epitaxy of InN on/in +c-GaN matrix and fabrication of fine-structure InN/GaN quantum wells: Role of high growth temperature
Thegrowth kinetics and properties of nominally 1-ML (monolayer)-thick InN wells on/in +c-GaN matrix fabricated using dynamic atomic layerepitaxy (D-ALEp) by plasma-assisted molecular beamepitaxy were systematically studied, with particular attention given to the effects ofgrowth temperature. Attention was also given to how and where the ∼1-ML-thick InN layers were frozen or embedded on/in the +c-GaN matrix. The D-ALEp of InN onGaN was a two-stage process; in the 1st stage, an “In+N” bilayer/monolayer was formed on theGaN surface, while in the 2nd, this was capped by aGaN barrier layer. Each process was monitoredin-si...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Akihiko Yoshikawa, Kazuhide Kusakabe, Naoki Hashimoto, Eun-Sook Hwang, Daichi Imai and Takaomi Itoi Source Type: research
Strong piezoelectric response in stable TiZnN2, ZrZnN2, and HfZnN2 found by ab initio high-throughput approach
Thephase diagrams of the Ti-Zn-N, Zr-Zn-N, and Hf-Zn-N systems are determined using large-scale high-throughput density functional calculations. Thermodynamically stable ordered phases of TiZnN2, ZrZnN2, and HfZnN2 have been found to be promising candidates inpiezoelectric devices/applications for energy harvesting. The identified stable phase of TiZnN2 is an ordered wurtzite superstructure, and the stable phases of ZrZnN2 and HfZnN2 have a layeredstructure with alternating tetrahedral ZnN and octahedral (Zr, Hf)N layers. All of the TMZnN2 (TM = Ti,Zn, Hf)structures exhibit electronicbandgaps and largepiezoelectric co...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: C. Tholander, C. B. A. Andersson, R. Armiento, F. Tasn ádi and B. Alling Source Type: research
Infrared laser ablation of polymeric nanocomposites: A study of surface structure and plume formation
The behavior ofcarbon nanotubecomposites subjected to laser pulseheating with a 1070 nm variable pulse duration laser has been studied. Previous work has shown thatcarbon nanotubecomposites form a protective network on the surface of acomposite, which reduces heat input to the underlyingpolymer and slows mass loss. In this work, we have studied the interaction between the incident laser and the plume formed above thecomposite. We have correlated these interactions with features observed in the time-resolved mass loss data and confirmed them with observations using high-speed video of the laser irradiations. Beam interac...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: S. F. Bartolucci, M. J. Miller and J. M. Warrender Source Type: research
Performance degradation of superlattice MOSFETs due to scattering in the contacts
Ideal, completely coherent quantum transport calculations had predicted thatsuperlatticeMOSFETs (SL-MOSFET) may offer steep subthreshold swing performance below 60 mV/dec to around 39 mV/dec. However, the highcarrier density in thesuperlattice source suggests thatscattering may significantly degrade the ideal device performance. Such effects ofelectron scattering and decoherence in the contacts of SL-MOSFETs are examined through a multi-scale quantum transportmodel developed in NEMO5. Thismodel couples the NEGF-based quantumballistic transport in the channel to a quantum mechanicaldensity of states dominated reservoir...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Pengyu Long, Jun Z. Huang, Zhengping Jiang, Gerhard Klimeck, Mark J. W. Rodwell and Michael Povolotskyi Source Type: research
Cherenkov terahertz surface plasmon excitation by an electron beam over an ultrathin metal film
The mechanism of Cherenkov excitation of terahertz (THz)surfaceplasma wave (SPW), by a relativistic electron beam propagating over an ultrathinmetalfilmdeposited onglass, is investigated. The SPW field falls off exponentially in vacuum as well asglass, while thesurface plasmon resonant frequency is lowered by the reduction offilm thickness. The SPW field causes density bunching of the beam leading to current modulation and generation ofTHz radiation via the Cherenkov interaction. The frequency of the THz decreases with the energy of the beam, whereas the growth rate increases. (Source: Journal of Applied Physics)
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Pawan Kumar, Rajeev Kumar and Satish Kumar Rajouria Source Type: research
Unraveling the strain state of GaN down to single nanowires
GaN nanowires (NWs)grown by molecular beam epitaxy are usually assumed free of strain in spite of different individual luminescence signatures. To ascertain this usual assumption, thec/a of aGaN NW assembly has been characterized using bothX-ray diffraction andRaman spectroscopy, with scaling themeasurement down to the single NW. Free-standing single NWs have been observed free of strain —defined as[c/a−(c/a)o]/(c/a)o—within the experimental accuracy amounting to 1.25 × 10−4. However, in the general case, a significant portion of the NWs is coalesced, generating an average tensile strain that can be partly relea...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Thomas Auzelle, Xavier Biquard, Edith Bellet-Amalric, Zhihua Fang, Herv é Roussel, Ana Cros and Bruno Daudin Source Type: research
Role of oxygen and nitrogen in n-type microcrystalline silicon carbide grown by hot wire chemical vapor deposition
N-type microcrystallinesiliconcarbide ( μc-SiC:H(n)) deposited by hot wire chemical vapor deposition provides advantageous opto-electronic properties for window layer material in silicon-basedthin-filmsolar cells andsiliconheterojunctionsolar cells. So far, it is known that the dark conductivity ( σd) increases with the increase in the crystallinity of μc-SiC:H(n)films. However, due to the fact that no activedoping source is used, the mechanism of electrical transport in these films is still under debate. It is suggested that unintentionaldoping by atmospheric oxygen (O) or nitrogen (N) contamination plays an important ...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: Manuel Pomaska, Jan Mock, Florian K öhler, Uwe Zastrow, Martina Perani, Oleksandr Astakhov, Daniela Cavalcoli, Reinhard Carius, Friedhelm Finger and Kaining Ding Source Type: research
Disentangling energetic and charge-carrier dynamic influences on the open-circuit voltage in bulk-heterojunction solar-cells
A combination of transient and static techniques has been applied to bulk-heterojunction solar-cells to gain insight into the influence ofcharge-carrier dynamics and of energy level shifts in the vicinity of thecathode on the open-circuit voltage.Devices with a different thermal-annealing history but with similar active layer-morphology were compared. P3HT:PC60BM bulk heterojunction solar-cells with a standard ITO/PEDOT:PSS/active-layer/Al were investigated. We show that the open-circuit voltage increase that occurs when a sample is annealed before or aftercathode deposition is due roughly one third to a shift between the ...
Source: Journal of Applied Physics - December 8, 2016 Category: Physics Authors: A. Chelouche, G. Magnifouet, A. Al Ahmad, N. Leclerc, T. Heiser and P. L évêque Source Type: research
