| 1. |
- Aggerstam, Thomas, et al.
(författare)
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Electron and hole capture cross-sections of Fe acceptors in GaN:Fe epitaxially grown on sapphire
- 2007
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 36:12, s. 1621-1624
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Tidskriftsartikel (refereegranskat)abstract
- Carrier trapping of Fe (3+)/Fe2+ deep acceptors in epitaxially grown GaN:Fe on sapphire was studied by time-resolved photoluminescence. For the investigated Fe doping levels on the order of 10(18) cm(-3), the luminescence decay times are strongly dependent on the Fe concentration, indicating that Fe centers act as predominant nonradiative recombination channels. Linear dependence of the decay time on the iron concentration allows estimation of the electron capture cross-section for the Fe3+ ions, which is equal to 1.9 x 10(-15) cm(2). The upper bound for the cross-section of the hole capture of Fe2+ was evaluated as 10 x 10(-15) cm
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| 2. |
- Chung, S. J., et al.
(författare)
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Magneto-transport properties of a GaMnAs-based ferromagnetic semiconductor trilayer structure grown on a ZnMnSe buffer
- 2008
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 37:6, s. 912-916
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Tidskriftsartikel (refereegranskat)abstract
- Magneto-transport properties have been investigated in a ferromagnetic GaMnAs/GaAlAs/GaMnAs semiconductor trilayer structure grown on a ZnMnSe buffer layer. The presence of the ZnMnSe buffer leads to the formation of a spin-valve-like structure, which provides the opportunity to investigate spin scattering effects by Hall resistance and magnetoresistance (MR) measurements in the current-in-plane (CIP) configuration. The Curie temperature (T c) and coercivity of the bottom GaMnAs layer are observed to be different from those of the top GaMnAs layer due to the proximity effect between the ferromagnetic GaMnAs and paramagnetic ZnMnSe layers. A two-step behavior is observed in the hysteresis loops of the Hall resistance, indicating that the coercive fields are different in the two GaMnAs layers in the trilayer structure. The magnetoresistance (MR) measured simultaneously with the Hall resistance shows a sudden increase in the field region where the magnetization of the two GaMnAs layers is different. Although the MR ratio was observed to be only 0.04% in our trilayer structure (due to the experimental CIP configuration), the study clearly demonstrates the presence of spin scattering in a trilayer ferromagnetic semiconductor structure grown on a ZnMnSe buffer. © 2008 TMS.
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| 3. |
- Hofmann, T., et al.
(författare)
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Optical hall effect in hexagonal InN
- 2008
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 37:5, s. 611-615
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Tidskriftsartikel (refereegranskat)abstract
- Measurements of the optical Hall effect in naturally doped high-quality wurtzite-structure InN thin films by generalized ellipsometry reveal that both the surface and the interior (bulk) free electron densities decrease with power-law dependencies on the film thickness. We discover a significant deviation between the bulk electron and dislocation densities. This difference is attributed here to the existence of surface defects with activation mechanism different from bulk dislocations and identifies the possible origin of the so far persistent natural n-type conductivity in InN. We further quantify the anisotropy of the Gamma-point effective mass.
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| 4. |
- Johansson, Christian, et al.
(författare)
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Broadband dielectric characterization of a silicone elastomer
- 2007
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 36:9, s. 1206-1210
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of an electronics grade silicone elastomer have been investigated in the frequency intervals 0.1 Hz to 1 MHz at −150°C to 100°C and from 7 GHz to 18 GHz at room temperature. The measurements were performed with a dielectric spectrometer for the low frequency range and with a waveguide setup for the high frequency range. The results are discussed in terms of performance and usability of the material in electronic packaging. Minor direct current (dc) conduction has been observed at high temperatures and is probably related to low levels (ppm) of ionic impurities.
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| 5. |
- Kim, Joo-Hyung, et al.
(författare)
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Wet etching study of La-0.67(Sr0.5Ca0.5)(0.33)MnO3 films on silicon substrates
- 2008
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 37:3, s. 361-367
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Tidskriftsartikel (refereegranskat)abstract
- Wet etching of colossal magnetoresistive (CMR) perovskite La-0.67(Sr0.5Ca0.5)(0.33)MnO3 (LSCMO) films on Bi4Ti3O12/CeO2/yttrium-stabilized zirconia (YSZ)-buffered Si substrates was investigated using potassium hydroxide (KOH) and buffered hydrofluoric acid (BHF) solutions. X-ray diffraction (XRD) and scanning spreading resistance microscopy (SSRM) measurements revealed that the morphological roughness of the LSCMO films increases, while the electrical resistance roughness decreases, with increasing KOH etching time. The LSCMO films are highly chemically resistant to KOH solution; however, in the case of BHF etching, an etch rate of 22 nm/min was obtained with high selectivity over a photoresist mask.
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| 6. |
- Pearton, S. J., et al.
(författare)
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Ferromagnetism in transition-metal doped ZnO
- 2007
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 36:4, s. 462-471
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Forskningsöversikt (refereegranskat)abstract
- ZnO is an attractive candidate for spintronics studies because of its potential for exhibiting high Curie temperatures and the relative lack of ferromagnetic second phases in the material. In this paper, we review experimental results on transition-metal (TM) doping of ZnO and the current state of theories for ferromagnetism. It is important to re-examine some of the earlier concepts for spintronics devices, such as the spin field-effect transistor, to account for the presence of the strong magnetic field that has deleterious effects. In some of these cases, the spin device appears to have no advantage relative to the conventional charge-control electronic analog. We have been unable to detect optical spin polarization in ZnO.
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| 7. |
- Virshup, Ariel, et al.
(författare)
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Investigation of Thermal Stability and Degradation Mechanisms in Ni-Based Ohmic Contacts to n-Type SiC for High-Temperature Gas Sensors
- 2009
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 0361-5235 .- 1543-186X. ; 38:4, s. 569-573
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the thermal stability of Pt/TaSi (x) /Ni/SiC ohmic contacts, which have been implemented in SiC-based gas sensors developed for applications in diesel engines and power plants. The contacts remained ohmic on lightly doped n-type (similar to 1 x 10(16) cm(-3)) 4H-SiC for over 1000 h in air at 300A degrees C. Although a gradual increase in specific contact resistance from 3.4 x 10(-4) Omega cm(2) to 2.80 x 10(-3) Omega cm(2) was observed, the values appeared to stabilize after similar to 800 h of heating in air at 300A degrees C. The contacts heated at 500A degrees C and 600A degrees C, however, showed larger increases in specific contact resistance followed by nonohmic behavior after 240 h and 36 h, respectively. Concentration profiles from Auger electron spectroscopy and electron energy-loss spectroscopy show that loss of ohmic behavior occurs when the entire tantalum silicide layer has oxidized.
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| 8. |
- Willander, Magnus, et al.
(författare)
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Some silicon-based heterostructures for optical applications
- 2005
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Ingår i: Journal of Electronic Materials. - : Springer Science Business Media. - 0361-5235 .- 1543-186X. ; 34:5, s. 515-521
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we will present our recent research on the growth and characterization of some Si-based heterostructures for optical and photonic devices. The heterostructures to be discussed are ZnO nanorods on Si, SiO2, and other substrates such as SiN and sapphire. We will also consider strained Si1-xGex/Si heterostructures for Si optoelectronics. The performance and functionality extension of Si technology for photonic applications due to the development of such heterostructures will be presented. We will focus on the results of structural and optical characterization in relation to device properties. The structural characterization includes x-ray diffraction for assessment of the crystallinity and stress in the films and secondary ion mass spectrometry for chemical analysis. The optical properties and electronic structure were investigated by using photoluminescence. The device application of these thin film structures includes detectors, lasers, and light emitting devices. Some of the Si-based heterostructures to be presented include devices emitting and detecting up to the blue-green and violet wave lengths.
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| 9. |
- Zou, Xiangdong, et al.
(författare)
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Nanoparticles of the Lead-free Solder Alloy Sn-3.0Ag-0.5Cu with Large Melting Temperature Depression
- 2009
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Ingår i: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 38:2, s. 351-355
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Tidskriftsartikel (refereegranskat)abstract
- Due to the toxicity of lead (Pb), Pb-containing solder alloys are being phased out from the electronics industry. This has lead to the development and implementation of lead-free solders. Being an environmentally compatible material, the lead-free Sn-3.0Ag-0.5Cu (wt.%) solder alloy is considered to be one of the most promising alternatives to replace the traditionally used Sn-Pb solders. This alloy composition possesses, however, some weaknesses, mainly as a result of its higher melting temperature compared with the Sn-Pb solders. A possible way to decrease the melting temperature of a solder alloy is to decrease the alloy particle size down to the nanometer range. The melting temperature of Sn-3.0Ag-0.5Cu lead-free solder alloy, both as bulk and nanoparticles, was investigated. The nanoparticles were manufactured using the self-developed consumable-electrode direct current arc (CDCA) technique. The melting temperature of the nanoparticles, with an average size of 30 nm, was found to be 213.9°C, which is approximately 10°C lower than that of the bulk alloy. The developed CDCA technique is therefore a promising method to manufacture nanometer-sized solder alloy particles with lower melting temperature compared with the bulk alloy.
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| 10. |
- Ding, Feng, 1970, et al.
(författare)
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Molecular dynamics study of bamboo-like carbon nanotube nucleation
- 2006
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Ingår i: JOURNAL OF ELECTRONIC MATERIALS. - 0361-5235. ; 35:2, s. 207-210
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) simulations based on an empirical potential energy surface were used to study the nucleation of bamboo-like carbon nanotubes (BCNTs). The simulations reveal that inner walls of the bamboo structure start to nucleate at the junction between the outer nanotube wall and the catalyst particle. In agreement with experimental results, the simulations show that BCNTs nucleate at higher dissolved carbon concentrations (i.e., feedstock pressures) than those where nonbamboo-like carbon nanotubes are nucleated.
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