jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 May 2012

Volume 111, Issue 10, Articles (10xxxx)

Issue Cover Spotlight Figure

J. Appl. Phys. 111, 102701 (2012); http://dx.doi.org/10.1063/1.4712272 (2 pages)

Ram Katiyar, Orlando Auciello, and Reji Thomas
Enlarge Image | Read More
Page 1 of 8 Pages Next Page | Jump to Page
back to top
RSS Feeds
back to top Preface
FREE

Preface to the International Symposium on Integrated Functionalities (ISIF 2010) Special Issue of Journal of Applied Physics Science and Technology of Integrated Functionalities

Ram Katiyar, Orlando Auciello, and Reji Thomas

J. Appl. Phys. 111, 102701 (2012); http://dx.doi.org/10.1063/1.4712272 (2 pages)

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Show PACS
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.80.-e Ferroelectricity and antiferroelectricity

Improved multiferroic properties in Sm-doped BiFeO3 thin films deposited using chemical solution deposition method

S. K. Singh, C. V. Tomy, T. Era, M. Itoh, and H. Ishiwara

J. Appl. Phys. 111, 102801 (2012); http://dx.doi.org/10.1063/1.4714650 (4 pages) | Cited 3 times

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Sm-substituted (0% to 10%) BiFeO3 thin films were fabricated by chemical solution deposition on Pt/Ti/SiO2/Si substrates. X-ray diffraction analysis revealed that no secondary phase appeared even if Bi atoms were substituted with Sm atoms up to 10 at. %. 7.5 at. % Sm-substituted films show improved electrical properties and substitution was effective in improving the coercive field in the films. Sm-substitution shows improved ferroelectric as well as magnetic properties of the films. There is a noticeable reduction in the leakage current density (10−4 A/cm2) and increase in the polarization (70 μC/cm2) when the Sm concentration is kept around 7.5%. The magnetic moment obtained from the saturated magnetization curves shows a value of 0.3 μB/Fe compared to 0.04 μB/Fe for the parent compound. The results are important since it increases the potential of the material as a multiferroic compound.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
77.22.Ej Polarization and depolarization
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.Nv Multiferroic/magnetoelectric films
75.30.Cr Saturation moments and magnetic susceptibilities
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Room temperature structural, morphological, and enhanced ferroelectromagnetic properties of xBa0.7Ca0.3TiO3−(1−x)BaFe0.2Ti0.8O3 multiferroic composites

V. S. Puli, I. Coondoo, N. Panwar, A. Srinivas, and R. S. Katiyar

J. Appl. Phys. 111, 102802 (2012); http://dx.doi.org/10.1063/1.4714657 (4 pages) | Cited 1 time

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Iron substituted barium titanate (BaTiO3, BT) has been found to exhibit both ferroelectric and ferromagnetic behavior at room temperature [Xu et al., Phys. Rev. B 79, 134109 (2009)]. However, ferroelectric properties of Fe-doped BT are not as pronounced as those of pure BT. It happens because iron doping causes hexagonal phase formation which inhibits ferroelectricity. We observed enhanced ferroelectric properties in x(Ba0.7Ca0.3)TiO3/(1−x)Ba(Fe0.2Ti0.8)O3 [(BCT-BFT) where x = 0.10, 0.15, 0.20] composites while maintaining the ferromagnetic characteristics. Structural and morphological studies reveal that composite with low content of BCT possesses dominating hexagonal phase, whereas tetragonal phase is more prominent in composite with higher BCT concentration. Such composite systems with enhanced ferroelectric and ferromagnetic behavior may be useful for room temperature multiferroic devices.
Show PACS
75.85.+t Magnetoelectric effects, multiferroics
77.80.bg Compositional effects
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
77.84.Lf Composite materials
68.35.bt Other materials

Deposition of stress free c-axis oriented LiNbO3 thin film grown on (002) ZnO coated Si substrate

Swati Shandilya, Monika Tomar, and Vinay Gupta

J. Appl. Phys. 111, 102803 (2012); http://dx.doi.org/10.1063/1.4714664 (6 pages) | Cited 1 time

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
C-axis oriented lithium niobate thin films have been deposited on Si substrate using RF sputtering technique. A thin buffer layer of c-axis (002) oriented ZnO on Si substrate has been used as a nucleating layer to promote the growth of (006) oriented LiNbO3 film. The processing gas composition and pressure are found to be very critical in obtaining stress free LiNbO3 film having desired (006) orientation. The LiNbO3 films deposited under unique combination of sputtering pressure (10 mTorr) and argon percentage (80%) in reactive gas (Ar + O2) composition become almost stress free having lattice parameter (1.3867 Å) close to the bulk value. The observed variation in the structural properties and optical phonon modes observed by Raman spectroscopic studies of the oriented LiNbO3 thin film with stress has been correlated with growth kinetics.
Show PACS
68.55.aj Insulators
78.30.Hv Other nonmetallic inorganics
78.66.Nk Insulators
81.15.Cd Deposition by sputtering
63.20.D- Phonon states and bands, normal modes, and phonon dispersion

Fe doped ZnO thin film for mediator-less biosensing application

Shibu Saha, Monika Tomar, and Vinay Gupta

J. Appl. Phys. 111, 102804 (2012); http://dx.doi.org/10.1063/1.4714670 (5 pages)

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fe doped ZnO (FZO) thin film is prepared by pulsed laser deposition for its application as mediator-less biosensing matrix. Fe doping introduces redox centre in ZnO along with shallow donor level and promotes the electron transfer capability due to substitution of Fe at Zn sites. Glucose oxidase (GOx), chosen as model enzyme, was immobilized on surface of the prepared matrix. Cyclic voltammetry and photometric assay show that the developed bio-electrode, GOx/FZO/indium tin oxide/Glass is sensitive to glucose concentration with enhanced response (0.2 µA mM−1 cm−2) and low Km (3.01 mM). The results show promising application of Fe doped ZnO thin film as an attractive matrix for mediator-less biosensing.
Show PACS
87.80.Kc Electrochemical techniques
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
82.45.Fk Electrodes
82.47.Rs Electrochemical sensors
82.80.Fk Electrochemical methods
87.14.ej Enzymes

Structural and magnetic properties of N doped ZnO thin films

Kajal Jindal, Monika Tomar, R. S. Katiyar, and Vinay Gupta

J. Appl. Phys. 111, 102805 (2012); http://dx.doi.org/10.1063/1.4714686 (5 pages) | Cited 1 time

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Experimental investigations and first-principle calculations based on density functional theory are effectively combined to shed light on origin of room temperature ferromagnetism in nitrogen doped ZnO (ZnO:N) based intrinsic dilute magnetic semiconductors. ZnO:N thin films grown by pulsed laser deposition show a well defined M-H hysteresis loop at room temperature, reflecting ferromagnetic behavior in contrast to undoped ZnO thin films grown under the same processing condition. Isotropic behavior of magnetism in ZnO:N reveals the dominant contribution of N incorporation on the magnetism and is attributed to p-p interaction between nitrogen and neighboring oxygen atoms having potential for room temperature spintronic applications.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
71.20.Nr Semiconductor compounds
75.50.Dd Nonmetallic ferromagnetic materials

ZnO nanowire based visible-transparent ultraviolet detectors on polymer substrates

Hongbin Yu, Ebraheem Ali Azhar, Tej Belagodu, Swee Lim, and Sandwip Dey

J. Appl. Phys. 111, 102806 (2012); http://dx.doi.org/10.1063/1.4714698 (5 pages) | Cited 2 times

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The fabrication and characterization of fully visible-transparent and flexible ultraviolet (UV) detectors, on polyethylene 2,6-naphthalate (PEN) with active channels of zinc oxide nanowires and ohmic indium tin oxide contacts, are reported and discussed. The fabricated detector has an average transmittance of 80% in the visible spectral range and is most responsive at or below 370 nm, the onset of UV light, with a UV/vis rejection ratio of 1.42 × 103. A five orders of magnitude difference in the photocurrent, between UV illumination and dark conditions, are also observed. The single-sided UV response further shows that the PEN substrate performs well as a UV reflector. The noise analysis on the nanowire UV detector indicates a noise equivalent power and detectivity (D*) of 5.88 × 10−13 WHz−0.5 and 2.13 × 109 cm Hz0.5 W−1, respectively.
Show PACS
85.60.Gz Photodetectors (including infrared and CCD detectors)

Threshold resistive and capacitive switching behavior in binary amorphous GeSe

Doo Seok Jeong, Hyungkwang Lim, Goon-Ho Park, Cheol Seong Hwang, Suyoun Lee, and Byung-ki Cheong

J. Appl. Phys. 111, 102807 (2012); http://dx.doi.org/10.1063/1.4714705 (8 pages) | Cited 3 times

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A threshold switching (TS) event in a binary amorphous GeSe film placed between Pt top and bottom electrodes was examined. This GeSe film exhibits fast (<40 ns) TS behavior. The observed TS of the resistance was found to be accompanied with the TS of the capacitance. A mechanism for the TS of the GeSe film was suggested by revisiting the previous controversy about the thermal versus non-thermal electronic mechanism. The non-thermal electronic mechanism envisaging the double-injection of electronic carriers can qualitatively account for the measured threshold resistive and capacitive switching, whereas the TS behavior simulated using the thermal mechanism is inconsistent with the experimental observation.
Show PACS
72.60.+g Mixed conductivity and conductivity transitions
73.61.Jc Amorphous semiconductors; glasses
81.05.Gc Amorphous semiconductors

Materials for phase-change memory with elevated temperature stability

Kin-Fu Kao, Yung-Ching Chu, Ming-Jinn Tsai, and Tsung-Shune Chin

J. Appl. Phys. 111, 102808 (2012); http://dx.doi.org/10.1063/1.4714711 (6 pages) | Cited 1 time

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Thermal stability is one of the key issues in phase-change memory. We try to tackle it by developing new compositions based on Ga-Te-Sb system. Thermal stability is exemplified using Ga18Te12Sb70 which shows crystallization-temperature (Tx) 248 °C and activation energy of non-isothermal crystallization 5.9 eV. Films were isothermally soaked at 5 ∼ 30 °C below Tx to estimate the failure-time when electrical resistance dropped to a half of the original. Arrhenius plot attained using logarithm failure-time versus reciprocal temperature were extrapolated to the temperature corresponding to 10-year failure (T10y) as 183 °C. Pre-crystallization structure upon heating to 2 ∼ 5 °C below Tx reflects stable amorphous phase of the alloy up to at least 240 °C. Memory-cells made of Ga18Te12Sb70 can be set-reset at 20 ∼ 500 ns with electrical currents around 66% those of our Ge2Sb2Te5 cells. We suggest that compositions Ga18–25Te8–12Sb67–70 are optimal to ensure Tx > 240 °C, T10y > 180 °C and with low operation-currents.
Show PACS
84.30.Sk Pulse and digital circuits

A comparative study of ultraviolet photoconductivity relaxation in zinc oxide (ZnO) thin films deposited by different techniques

Harish Kumar Yadav and Vinay Gupta

J. Appl. Phys. 111, 102809 (2012); http://dx.doi.org/10.1063/1.4714715 (5 pages) | Cited 1 time

Online Publication Date: 16 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photoresponse characteristics of ZnO thin films deposited by three different techniques namely rf diode sputtering, rf magnetron sputtering, and electrophoretic deposition has been investigated in the metal-semiconductor-metal (MSM) configuration. A significant variation in the crystallinity, surface morphology, and photoresponse characteristics of ZnO thin film with change in growth kinetics suggest that the presence of defect centers and their density govern the photodetector relaxation properties. A relatively low density of traps compared to the true quantum yield is found very crucial for the realization of practical ZnO thin film based ultraviolet (UV) photodetector.
Show PACS
72.40.+w Photoconduction and photovoltaic effects
78.66.Hf II-VI semiconductors
81.05.Dz II-VI semiconductors
81.15.Cd Deposition by sputtering
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.bg Semiconductors

Combinatorial growth of oxide nanoscaffolds and its influence in osteoblast cell adhesion

Claudia Y. Acevedo-Morantes, Roberto A. Irizarry-Ortiz, Pablo G. Caceres-Valencia, Surinder P. Singh, and Jaime E. Ramirez-Vick

J. Appl. Phys. 111, 102810 (2012); http://dx.doi.org/10.1063/1.4714727 (7 pages) | Cited 1 time

Online Publication Date: 17 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report a novel method for high-throughput investigations on cell-material interactions based on metal oxide nanoscaffolds. These scaffolds possess a continuous gradient of various titanium alloys allowing the compositional and morphological variation that could substantially improve the formation of an osseointegrative interface with bone. The model nanoscaffold has been fabricated on commercially pure titanium (cp-Ti) substrate with a compositional gradients of tin (Sn), chromium (Cr), and niobium (Nb) deposited using a combinatorial approach followed by annealing to create native oxide surface. As an invitro test system, the human fetal osteoblastic cell line (hFOB 1.19) has been used. Cell-adhesion of hFOB 1.19 cells and the suitability of these alloys have been evaluated for cell-morphology, cell-number, and protein adsorption. Although, cell-morphology was not affected by surface composition, cell-proliferation rates varied significantly with surface metal oxide composition; with the Sn- and Nb-rich regions showing the highest proliferation rate and the Cr-rich regions presenting the lowest. The results suggest that Sn and Nb rich regions on surface seems to promote hFOB 1.19 cell proliferation and may therefore be considered as implant material candidates that deserve further analysis.
Show PACS
87.17.Rt Cell adhesion and cell mechanics
87.15.km Protein-protein interactions
87.15.R- Reactions and kinetics
87.17.Pq Morphogenesis

Dielectric properties and electrical conduction of high-k LaGdO3 ceramics

S. P. Pavunny, R. Thomas, A. Kumar, N. M. Murari, and R. S. Katiyar

J. Appl. Phys. 111, 102811 (2012); http://dx.doi.org/10.1063/1.4714721 (5 pages) | Cited 2 times

Online Publication Date: 18 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The temperature and frequency dependent dielectric properties and leakage conduction mechanism in LaGdO3 (LGO) ceramics have been studied, and this material has been identified as a potential high-k candidate for the future complementary metal-oxide-semiconductor (CMOS) and dynamic random access memory (DRAM) technology nodes. The dielectric constant and the loss tangent at 100 kHz were ∼21.5 and ∼0.003, respectively, at ambient conditions without any significant temperature and voltage dependence. The ac conductivity shows the typical features of universal dynamic response (UDR) and obey the double power law σac = σdc+Aωn1+Bωn2 with three types of temperature dependent conduction processes involved; (i) a dc plateau (< 3 kHz) due to long range translational hopping, (ii) a mid frequency region due to the short range hopping (3–100 kHz), and (iii) a high frequency region due to localized or reorientational hopping (100–1000 kHz). The temperature dependent dc conductivity follows the Arrhenius relation with activation energies of 0.05 eV in the 200–400 K range and 0.92 eV in the 400–600 K range. The leakage current behavior reveals bulk limited Poole-Frenkel (PF) conduction mechanism and the estimated optical dielectric constant (ɛ∞) is 3.6.
Show PACS
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
72.20.Ee Mobility edges; hopping transport
72.20.Ht High-field and nonlinear effects

Determination of maximum power transfer conditions of bimorph piezoelectric energy harvesters

Mahmoud Al Ahmad, A. M. Elshurafa, K. N. Salama, and H. N. Alshareef

J. Appl. Phys. 111, 102812 (2012); http://dx.doi.org/10.1063/1.4714644 (4 pages)

Online Publication Date: 24 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, a method to find the maximum power transfer conditions in bimorph piezoelectric-based harvesters is proposed. Explicitly, we derive a closed form expression that relates the load resistance to the mechanical parameters describing the bimorph based on the electromechanical, single degree of freedom, analogy. Further, by taking into account the intrinsic capacitance of the piezoelectric harvester, a more descriptive expression of the resonant frequency in piezoelectric bimorphs was derived. In interest of impartiality, we apply the proposed philosophy on previously published experimental results and compare it with other reported hypotheses. It was found that the proposed method was able to predict the actual optimum load resistance more accurately than other methods reported in the literature.
Show PACS
84.60.-h Direct energy conversion and storage
back to top
RSS Feeds
back to top Lasers, Optics, and Optoelectronics

Inhomogeneous nanostructured honeycomb optical media for enhanced cathodo- and under-x-ray luminescence

N. V. Gaponenko, V. S. Kortov, M. V. Rudenko, V. A. Pustovarov, S. V. Zvonarev, A. I. Slesarev, I. S. Molchan, G. E. Thompson, L. S. Khoroshko, and S. Ya. Prislopskii

J. Appl. Phys. 111, 103101 (2012); http://dx.doi.org/10.1063/1.4717740 (6 pages) | Cited 1 time

Online Publication Date: 17 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Photo-, radio-, and pulse cathodoluminescence spectra from sol-gel derived titania, doped with strontium and terbium, deposited on porous anodic alumina (PAA) films are reported. The morphology and qualitative elemental depth distributions have been examined by transmission electron microscopy, scanning electron microscopy, and radio-frequency glow discharge optical emission spectroscopy. PAA films with pore and cell sizes ranging from 170 to 190 and 240 to 270 nm, respectively, have been generated on aluminum and monocrystalline silicon substrates followed by spin-on sol-gel derived coating with the subsequent thermal treatment. The resultant PAA surface is not coated with a continuous xerogel film; the xerogel is mainly distributed near the pore bases, leaving much of the pore volume unfilled. The xerogel/PAA structures reveal terbium-related luminescence under x-ray excitation and cathodoluminescence. The same xerogels generated on monocrystalline silicon revealed no cathode- or under-x-ray luminescence. Thus, PAA enhances strongly the cathode- and under x-ray luminescence from terbium and strontium-doped titania xerogels confined in the porous matrix. The fabricated structures are considered as a type of low-cost, thin-film convertor of x-rays, and cathode ray irradiation into visible light, with an average cell size of the convertor of about 250 nm.
Show PACS
81.07.Bc Nanocrystalline materials
42.70.-a Optical materials
78.55.Hx Other solid inorganic materials
78.60.Hk Cathodoluminescence, ionoluminescence

Plasmonic dispersion engineering of coupled metal nanoparticle-film systems

Jeff DiMaria and Roberto Paiella

J. Appl. Phys. 111, 103102 (2012); http://dx.doi.org/10.1063/1.4717763 (5 pages) | Cited 1 time

Online Publication Date: 17 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The plasmonic dispersion properties of thin silver films in close proximity of square-periodic arrays of silver nanocylinders are investigated via transmission measurements and numerical simulations. Due to their nanoscale thicknesses, these films support hybrid surface plasmon modes extended across both interfaces, whose dispersion curves exhibit a large geometrically tunable energy splitting. Furthermore, the spatial and spectral overlap between these modes and the nanoparticles’ localized plasmonic resonances produces an additional anticrossing in the dispersion spectrum. The resulting plasmonic excitations are attractive for applications given their wide tunability, coupling to free-space radiation, and ability to extend into an optically active substrate.
Show PACS
73.22.Lp Collective excitations
78.66.Bz Metals and metallic alloys
78.68.+m Optical properties of surfaces
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Optical switch based on electrowetting liquid lens

Lei Li, Chao Liu, Hua-Rong Peng, and Qiong-Hua Wang

J. Appl. Phys. 111, 103103 (2012); http://dx.doi.org/10.1063/1.4717715 (4 pages) | Cited 1 time

Online Publication Date: 18 May 2012

Full Text: Read Online (HTML) | Download PDF

multimedia

Show Abstract
In this paper, we propose an optical switch based on an electrowetting liquid lens. The device consists of an electrowetting liquid lens and a non-transparent cap with a pin hole. When the lens is actuated to be positive, the incident light can be converged on the pin hole and pass through the hole with less attenuation. When the lens is deformed to be negative, the incident light is diverged and most of light is blocked by the cap. Our results show that the system can provide high contrast ratio (∼800:1) and reasonable response time (∼88 ms). The proposed optical switch has potential application in light shutters, variable optical attenuators, and adaptive irises.
Show PACS
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
42.79.Bh Lenses, prisms and mirrors

A simple analysis of interband absorption in quantum well structure of III-V ternary and quaternary semiconductors

Anup Dey, Biswajit Maiti, and Debasree Chanda (Sarkar)

J. Appl. Phys. 111, 103104 (2012); http://dx.doi.org/10.1063/1.4718414 (9 pages)

Online Publication Date: 18 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A simple generalized theory is presented for the determination of interband optical absorption coefficient (IOAC) around band edges, in quantum well (QW) structure of non-parabolic semiconducting materials whose band structures obey the three band model of Kane. The dependence of absorption coefficient on wave-vector (math) has also been investigated. IOAC has been calculated for a wide range of III–V compound semiconductors, such as InAs, InSb, Hg1−xCdxTe, and In1−xGaxAsyP1−y lattice matched to InP. It has been found that IOAC for QWs increases in steps with increasing photon energy and the positions of jumps of the coefficient are more closely spaced in the three band model of Kane than those with parabolic energy band approximations in all the cases. IOAC for QWs is largely dependent on the polarization direction of the incident light and on the well dimension as well. The expressions of IOAC presented in this article can easily be extended to incorporate the effects of different external conditions like strain, electric, and magnetic fields on IOAC. It has also been shown that under certain limiting conditions the expressions for IOAC reduces to the previously known results for wide band gap materials and this is the indication for it to be a generalized theory for IOAC.
Show PACS
78.67.De Quantum wells
73.21.Fg Quantum wells
71.20.Nr Semiconductor compounds
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Characterization of low temperature InGaAs-InAlAs semiconductor photo mixers at 1.55 μm wavelength illumination for terahertz generation and detection

I. Kostakis, D. Saeedkia, and M. Missous

J. Appl. Phys. 111, 103105 (2012); http://dx.doi.org/10.1063/1.4719052 (6 pages)

Online Publication Date: 21 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The structural, optical, and electrical properties of undoped and Be doped lattice matched InGaAs–InAlAs multiple quantum well structures, grown by molecular beam epitaxy (MBE) at low (∼250 °C) and normal (∼450 °C) growth temperatures, have been investigated in detail. Double crystal x-ray diffraction studies showed that the thickness of the low temperature (LT) grown quantum well (QW) layers decrease with post growth annealing, while the normal temperature grown QW layers retain their initial thickness. This behaviour is associated with the As precipitation and is the first evidence and report of a direct observation of this phenomenon in LT InGaAs–InAlAs QWs. Room temperature photoluminescence (PL) measurements revealed signs of optical activities in the LT undoped and lower doped structures suggesting that the native defects in LT InGaAs–InAlAs are not sufficient to completely inhibit band to band recombination. Optimal combination of doping, including a modulation doped structure, and post growth annealing temperature results in materials with sub-picoseconds lifetimes (<200 fs) and a resistivity of ∼107 Ω/sq, which is a high value for this material. The results imply the possibility of fabricating efficient photo-mixers operating at the telecom wavelength of 1.55 μm for THz imaging or other optoelectronic applications.
Show PACS
78.67.De Quantum wells
81.30.Mh Solid-phase precipitation
73.63.Hs Quantum wells

Improved terahertz quantum cascade laser with variable height barriers

Alpar Matyas, Reza Chashmahcharagh, Istvan Kovacs, Paolo Lugli, Karun Vijayraghavan, Mikhail A. Belkin, and Christian Jirauschek

J. Appl. Phys. 111, 103106 (2012); http://dx.doi.org/10.1063/1.4719071 (6 pages) | Cited 2 times

Online Publication Date: 21 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using an ensemble Monte-Carlo analysis, it is found that relaxing the constraint of identical barrier heights can result in an improved temperature performance. Exploiting this additional design degree of freedom, modified structures with non-uniform barrier heights are developed based on the current record temperature design. For an optimized structure with reduced diagonality, we predict an increase of 31 K for the maximum operating temperature. Furthermore, we develop improved designs with the same oscillator strength as for the reference design. Using a genetic algorithm for optimization, an improvement of the maximum operating temperature by 38 K is obtained. These results aim to show the potential of varying the barrier heigths for the design of high temperature performance terahertz quantum cascade lasers.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
84.40.-x Radiowave and microwave (including millimeter wave) technology
42.60.By Design of specific laser systems

Highly stable charge generation layers using caesium phosphate as n-dopants and inserting interlayers

Carola Diez, Thilo C. G. Reusch, Erwin Lang, Thomas Dobbertin, and Wolfgang Brütting

J. Appl. Phys. 111, 103107 (2012); http://dx.doi.org/10.1063/1.4720064 (7 pages) | Cited 1 time

Online Publication Date: 22 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Highly stable and efficient charge generation layers (CGLs) comprising caesium phosphate (Cs3PO4) doped 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as n-type organic semiconductor and molybdenum trioxide (MoO3) doped N,N′-di-(naphthalen-1-yl)-N,N′-diphenyl-benzidine (α-NPD) as p-type organic semiconductor, respectively, are presented. By inserting narrow-gap organic copper-phthalocyanine (CuPc) and wide-gap insulating aluminum oxide (Al2O3) as interlayer (IL), we show that the long-term stability of the CGL can be improved. The variation of the CuPc IL thickness yields an optimum of 8 nm as a trade-off between minimal operating voltage and maximum voltage stability of the CGL. Luminance-current density-voltage characteristics and lifetime measurements of stacked green organic light emitting diodes (OLEDs) confirm the functionality and high voltage stability of the presented CGL. The luminous efficacy of the stacked OLED compared to the non-stacked reference device is nearly unchanged. However, the lifetime of the stacked device is enhanced by a factor of 3.5. Consistent with our experimental findings, we propose a model of the energy-level diagram of a fully doped CGL with IL based on a field-assisted tunneling mechanism.
Show PACS
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
85.60.Jb Light-emitting devices
73.40.Gk Tunneling

Zinc oxide micro-spheres with faceted surfaces produced by laser ablation of zinc targets

Ming Chen, Xiangdong Liu, Yuehua Liu, and Mingwen Zhao

J. Appl. Phys. 111, 103108 (2012); http://dx.doi.org/10.1063/1.4720073 (4 pages)

Online Publication Date: 22 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the fabrication of ZnO micro-spheres using high-power laser ablation of Zn metal in the presence of oxygen gas background without use of any catalysts or additives. The centre-symmetric geometrical structures of ZnO micro-spheres exhibit clear pentagonal and hexagonal facets with different sizes. A discussion of the growth mechanisms based on a model of subsurface micro-explosion boiling followed by laser-surface sintering of assembled particles has been proposed to explain the formation of the ZnO micro-spheres.
Show PACS
81.65.Ps Polishing, grinding, surface finishing
68.35.bg Semiconductors
79.20.Eb Laser ablation
52.38.Mf Laser ablation
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Enhanced entanglement between a movable mirror and a cavity field assisted by two-level atoms

Yong-Hong Ma and Ling Zhou

J. Appl. Phys. 111, 103109 (2012); http://dx.doi.org/10.1063/1.4719075 (4 pages)

Online Publication Date: 22 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A scheme to generate stationary entanglement in a Fabry-Perot cavity with two-level atoms is proposed in the current paper. The mechanism through which radiation pressure can generate steady-state entanglement is also presented. Moreover, the bipartite entanglement in the field-mirror subsystem is quantified. Logarithmic negativity, which characterizes the entanglement between the two systems, is found to increase from 0.27 to 0.32 with the help of the atoms. Surprisingly, such macroscopic entanglement persists for environment temperatures of about 25 K in this system.
Show PACS
42.50.Wk Mechanical effects of light on material media, microstructures and particles
42.50.Dv Quantum state engineering and measurements
03.67.Bg Entanglement production and manipulation
42.79.Bh Lenses, prisms and mirrors

First-principles analysis of structural and opto-electronic properties of indium tin oxide

Madhvendra Nath Tripathi, Kazuhito Shida, Ryoji Sahara, Hiroshi Mizuseki, and Yoshiyuki Kawazoe

J. Appl. Phys. 111, 103110 (2012); http://dx.doi.org/10.1063/1.4719980 (7 pages)

Online Publication Date: 23 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Density functional theory (DFT) and DFT + U (DFT with on-site Coulomb repulsion corrections) calculations have been carried out to study the structural and opto-electronic properties of indium tin oxide (ITO) for both the oxidized and reduced environment conditions. Some of the results obtained by DFT calculations differ from the experimental observations, such as uncertain indication for the site preference of tin atom to replace indium atom at b-site or d-site, underestimation of local inward relaxation in the first oxygen polyhedra around tin atom, and also the improper estimation of electronic density of states and hence resulting in an inappropriate optical spectra of ITO. These discrepancies of theoretical outcomes with experimental observations in ITO arise mainly due to the underestimation of the cationic 4d levels within standard DFT calculations. Henceforth, the inclusion of on-site corrections within DFT + U framework significantly modifies the theoretical results in better agreement to the experimental observations. Within this framework, our calculations show that the indium b-site is preferential site over d-site for tin atom substitution in indium oxide under both the oxidized and reduced conditions. Moreover, the calculated average inward relaxation value of 0.16 Å around tin atom is in good agreement with the experimental value of 0.18 Å. Furthermore, DFT + U significantly modify the electronic structure and consequently induce modifications in the calculated optical spectra of ITO.
Show PACS
71.20.Ps Other inorganic compounds
78.30.Hv Other nonmetallic inorganics
78.40.Ha Other nonmetallic inorganics
61.66.Fn Inorganic compounds
71.15.-m Methods of electronic structure calculations
71.15.Mb Density functional theory, local density approximation, gradient and other corrections

Mode characterization of sub-micron equilateral triangular microcavity including material’s dispersion effects

C.-M. Lai, P. C. Yeh, and L.-H. Peng

J. Appl. Phys. 111, 103111 (2012); http://dx.doi.org/10.1063/1.4720580 (5 pages)

Online Publication Date: 25 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report the study of resonant modes in an equilateral triangular gallium nitride (GaN) microcavity, with the material’s dispersion taken into account. From the polarization-resolved photo-luminescence measurements, we observed the resonance of GaN bandedge emission with the cavity modes to be transverse magnetic-polarization active and characterized with a quality factor as high as ∼1000 in a GaN cavity of 0.75 µm side length. Using a finite difference time domain technique, we showed that these observations can be ascribed to the material’s dispersion effects. The latter can modify the cavity phase-matching condition, reduce the spectral bandwidth of the corresponding resonant modes and enhance the cavity quality factor by a factor more than three.
Show PACS
07.10.Cm Micromechanical devices and systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
02.60.-x Numerical approximation and analysis

Effect of Lorentz local field for optical second order nonlinear susceptibility in ZnO nanorod

Guan-Yu Zhuo (卓冠宇), Kuo-Jen Hsu (徐國仁), Tung-Yu Su (蘇東榆), Nan-Hsun Huang (黃南勛), Yang-Fang Chen (陳永芳), and Shi-Wei Chu (朱士維)

J. Appl. Phys. 111, 103112 (2012); http://dx.doi.org/10.1063/1.4721379 (6 pages)

Online Publication Date: 25 May 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nonlinear optical properties of ZnO nanorods (NRs) are strongly influenced by its dimension and aspect ratio. Size-dependent second harmonic generation (SHG) in ZnO NRs has been investigated with polarized excitations recently. However, detailed description to the SHG dependency with NR dimensions has not yet been given. In this paper, the relationship between rod diameter/length and corresponding χ(2) values based on Lorentz local field is established, both theoretically and experimentally, for the first time. Theoretically, Lorentz local field induced spectral red shift and the consequent dielectric constant modification is used to elucidate the size effect for χ(2) under the condition that both excitation and SHG wavelengths are far from the band gap. Experimentally, χ(2) of ZnO nanorods with various sizes is measured via Maker fringe technique, and the results fit well to our theory.
Show PACS
78.66.Hf II-VI semiconductors
42.65.An Optical susceptibility, hyperpolarizability
Page 1 of 8 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close