Applied Physics Letters
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Critical behavior in Ti-doped manganites LaMn1−xTixO3 (0.05⩽x⩽0.2) The critical properties of the ferromagnetic insulating system LaMn1−xTixO3 (0.05⩽x⩽0.2) are investigated based on the static magnetization measurements around Curie temperature TC. The values of critical exponents, derived from the magnetic data using the Kouvel-Fisher method, yield 0.359⩽β⩽0.378, 1.24⩽γ⩽1.29, and 4.11⩽δ⩽4.21 with a TC of 95–173K. The exponent values are close to those expected for three-dimensional Heisenberg ferromagnets with short-range interactions, and the magnetic transition is understood in the context of Griffiths phase, arising from the random-temperature effects.
Applied Physics Letters - Tập 91 Số 14 - 2007
Solution-cast films of polyaniline: Optical-quality transparent electrodes Optical-quality transparent conducting films of polyaniline (PANI) and of conducting polyblends of polyaniline with amorphous bulk polymers are described. Using functionalized protonic acids to induce solubility in common organic solvents, PANI and PANI polyblends can be cast from solution, in the conducting form, onto a variety of substrates. The resulting films are clear, and they combine low surface resistance with excellent transparency. By varying the thickness of the film and/or the volume fraction of PANI in the polyblend, the surface resistance can be controlled over an extraordinary broad range.
Applied Physics Letters - Tập 60 Số 22 - Trang 2711-2713 - 1992
Enhanced luminescence of Y3Al5O12:Ce3+ nanophosphor for white light-emitting diodes Results pertaining to the development of highly dispersible stand-alone particles of Ce3+-doped Y3Al5O12 nanophosphor and their luminescence are presented. The yellow light-emitting nanophosphor was produced as a result of a single-step auto-combustion process, which requires no auxiliary annealing treatments prior to any practical application. The structure, photoluminescence, and chromaticity of the powder nanophosphor samples with the compositions Y(3−x)Al5O12:xCe3+ (x=0.01–1) are featured in the letter. The nanophosphor absorbs light efficiently in the visible region of 400–500nm, and shows single broadband emission peaking at ∼560nm. The luminescence yield is almost analogous to the samples made from other conventional methods. Hence, it could be an apt candidate for generating white light when coupled to a blue light-emitting diode (λem=450nm).
Applied Physics Letters - Tập 89 Số 17 - 2006
Photostimulated luminescence in Eu-doped fluorochlorozirconate glass ceramics We report the synthesis of Eu2+- and chlorine-doped fluorozirconate glass-ceramics that show an intense photostimulated luminescence (PSL) after x-ray irradiation at room temperature. The PSL efficiency is up to 80% of that found in the well-known crystalline x-ray storage phosphor BaFBr:Eu2+, and it is the largest thus far reported for a glass-ceramic. We attribute the PSL to crystallites of orthorhombic BaCl2 that are formed after annealing above the glass temperature. Hexagonal BaCl2 crystallites are also observed after short annealing times, but they do not provide a measurable PSL signal. The photoluminescence peak from glass-ceramics containing orthorhombic BaCl2 crystallites occurs at 402 nm, and the stimulation band is centered at about 560 nm.
Applied Physics Letters - Tập 83 Số 3 - Trang 449-451 - 2003
Epitaxial Pb(Zr0.53Ti0.47)O3/LaNiO3 heterostructures on single crystal substrates Epitaxial near-stoichiometric ferroelectric Pb(Zr0.53Ti0.47)O3 thin films were fabricated on epitaxial metallic LaNiO3 electrodes deposited on (001) SrTiO3 and (001) LaAlO3 single crystal substrates by pulsed laser ablation. The P–E hysteresis loop of PZT in the trilayer of Ag/PZT/LNO/STO was measured using the Sawyer–Tower circuit. The remnant polarization Pr and coercive field Ec at room temperature were 30 μC/cm2 and 69.3 kV/cm (peak-to-peak voltage=30 V, 50 Hz), respectively.
Applied Physics Letters - Tập 69 Số 14 - Trang 2092-2094 - 1996
Optical transitions in cubic GaN investigated by spatially resolved cathodoluminescence Spatially resolved cathodoluminescence (CL) spectroscopy in connection with scanning electron microscopy performed on cubic (c) GaN between 5 and 300 K reveals that at low temperatures the CL spectra of c-GaN single crystals consist of four well-separated lines. The two lines highest in energy were previously identified as excitonic and donor-acceptor transitions, respectively. Here, we show that the lines lowest in energy are due to an additional free-to-bound transition, involving an impurity different from those related to the donor-acceptor transition, and its phonon replica. The CL spectra of c-GaN layers, while being rather broad, are composed of these four lines. Moreover, at 300 K the spectra of the layers and of the crystals are both dominated by the excitonic transition and closely resemble each other.
Applied Physics Letters - Tập 69 Số 6 - Trang 836-838 - 1996
Epitaxial SrRuO3 thin films on (001) SrTiO3 Highly conductive metallic oxide thin films of SrRuO3 with single crystalline quality have been grown on (001) SrTiO3 by using pulsed laser deposition. The films have a [00l] orientation with an in-plane relationship of [110]SrRuO3 // [100]SrTiO3. They have excellent metallic behavior with room temperature resistivity of ∼310 μΩ cm and a residual resistance ratio of about 7 at 4.2 K, the largest reported to date. A clear ferromagnetic transition at ∼147 K was detected by resistivity and magnetic measurements. However, the transition becomes blurred as the density-of-point defects increases in the films following a 400 keV proton irradiation with an accumulative dose up to ∼6.0×1016 ions/cm2.
Applied Physics Letters - Tập 71 Số 8 - Trang 1047-1049 - 1997
Optical constants of graphene layers in the visible range We show that the optical constants of graphene in the visible range can be estimated by means of a very simple procedure involving their consistence with universal optical conductivity and experimentally measured optical spectra, within the framework of Fresnel coefficients calculation. The obtained complex refractive index allows for accurate prediction of the optical behavior of graphene in the visible range, from the two-dimensional limit (single atomically thick graphene layer) to the bulk limit (graphite). Therefore, it may result very useful for quantitative optical analysis of graphene layers and graphitic structures in general.
Applied Physics Letters - Tập 94 Số 3 - 2009
Growth of high quality epitaxial Ge films on (100)Si by sputter deposition Expitaxial Ge films ∼1.5 μm thick, were grown on (100) Si substrates at relatively low temperatures, 470°C, by rf sputter deposition. Low-energy ion bombardment of the substrate and growing film during deposition provided compositional grading of the lattice mismatched interface. X-ray diffraction and electron channeling spectra indicated that the films were single crystals while Hall measurements showed them to be p type with p(300 K)≃1×1017 cm−3 and corresponding carrier mobilities, 1280 cm2/Vs, comparable to the best bulk crystals. The thickness of the compositionally graded junction was found by Auger electron spectroscopy depth profiling to be ∼200 nm. C-V measurements indicated that over this region the net acceptor concentration increased from 4×1014 cm−3 near the substrate surface to the bulk film value of 1×1017 cm−3. Large area p-n diodes exhibited reverse breakdown voltages of ⩾10 V.
Applied Physics Letters - Tập 40 Số 8 - Trang 696-698 - 1982
Growth and patterning of GaAs/Ge single crystal layers on Si substrates by molecular beam epitaxy Single crystal GaAs layers have been grown on Si substrates with an intermediate Ge layer. Both the Ge and subsequent GaAs are grown in situ by molecular beam epitaxy (MBE). Cross-sectional transmission electron microscopy studies show GaAs surface dislocation densities on the order of 107 cm−2. The quality of the GaAs is indicated by a mobility within 15% of that measured on GaAs/GaAs MBE structures doped at the same level. This material also exhibits a photoluminescence signal with a room-temperature intensity about 50% of GaAs grown on GaAs, and with a similar half-width. In this letter, electron diffraction, optical and electrical data are presented for n-type GaAs/Ge/Si structures. In addition, a selective lift-off technique is demonstrated, with possible applications in the development of monolithic GaAs/Si integrated circuits.
Applied Physics Letters - Tập 45 Số 3 - Trang 274-276 - 1984
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