APL Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

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

8 Jan 1990

Volume 56, Issue 2, pp. 103-200

Page 2 of 2 Pages Previous Page | Jump to Page

On‐demand atmospheric pressure storage system for AsH3 and PH3

R. S. Sillmon and J. A. Freitas

Appl. Phys. Lett. 56, 174 (1990); http://dx.doi.org/10.1063/1.103020 (3 pages) | Cited 3 times

Full Text: | Download PDF

Show Abstract
An on‐demand atmospheric pressure storage system for AsH3 and PH3, which eliminates the sudden release hazard associated with compressed gases, has been developed and tested with AsH3. The storage system is based on the adsorption of these gases into the microcavities of synthetic zeolites at 23 °C and subsequent desorption at higher temperatures. The adsorption isotherm and isobar of AsH3 on NaA and CaA zeolites were measured. At 23 °C and 760 Torr AsH3 pressure, an adsorption capacity of 25 wt. % (AsH3/zeolite) was measured for CaA zeolite. About 100% of the adsorbed AsH3 was recovered at desorption temperatures below 190 °C. Preliminary results of operating a 500 cc prototype AsH3‐zeolite storage system connected to an organometallic vapor phase epitaxy reactor for the growth of GaAs and AlGaAs show that the purity of the AsH3 is retained during the adsorption/desorption process.
Show PACS
06.60.Wa Laboratory safety procedures
68.03.Fg Evaporation and condensation of liquids
68.43.Mn Adsorption kinetics
81.15.Kk Vapor phase epitaxy; growth from vapor phase

Determination of donor and acceptor densities in high‐purity GaAs from photoluminescence analysis

Z. H. Lu, M. C. Hanna, D. M. Szmyd, E. G. Oh, and A. Majerfeld

Appl. Phys. Lett. 56, 177 (1990); http://dx.doi.org/10.1063/1.103021 (3 pages) | Cited 23 times

Full Text: | Download PDF

Show Abstract
We report a new analysis technique to determine the acceptor density NA and the donor density ND in high‐purity GaAs from 10 K photoluminescence (PL) measurements. For both n‐type and p‐type samples, we find that NA/ND is related to the excitonic intensity ratio rx=I(A0,X)/I(D0,X) by NA/ND=0.89rx−0.06. In addition, NA can be determined from NA=1014IA, where IA is the emission intensity of the donor‐acceptor pair transition normalized to the intensity of the unresolved exciton peak. Therefore, for n‐type and p‐type material with an impurity density 1013–1016 cm−3, NA and ND can be determined solely from a 10 K PL measurement. The advantage of this technique lies in its nondestructive nature and its applicability to situations where Hall measurements are not possible or suitable.
Show PACS
71.55.Eq III-V semiconductors
71.35.-y Excitons and related phenomena
78.55.Cr III-V semiconductors
72.20.Fr Low-field transport and mobility; piezoresistance

Distortion of excitonic emission bands due to self‐absorption in ZnSe epilayers

Khalid Shahzad and David A. Cammack

Appl. Phys. Lett. 56, 180 (1990); http://dx.doi.org/10.1063/1.103022 (3 pages) | Cited 12 times

Full Text: | Download PDF

Show Abstract
In this letter we investigate the influence of self‐absorption on the excitonic emission spectra of ZnSe epitaxial layers grown by molecular beam epitaxy on GaAs substrates. We observe that, very often, samples grown under identical conditions show a widely ranging ratio of neutral donor‐bound‐exciton to free‐exciton intensities in photoluminescence (PL). We present experimental evidence to show that these differences can arise from the variations in the epilayer thickness and detailed PL experimental conditions and do not necessarily represent the layer‐to‐layer purity fluctuations, as the spectral line shapes may suggest.
Show PACS
71.35.-y Excitons and related phenomena
73.20.At Surface states, band structure, electron density of states
78.55.Et II-VI semiconductors
78.66.Fd III-V semiconductors
78.66.Hf II-VI semiconductors

Calcium substitution at yttrium site in YBa2Cu3Oy

M. R. Chandrachood, I. S. Mulla, S. M. Gorwadkar, and A. P. B. Sinha

Appl. Phys. Lett. 56, 183 (1990); http://dx.doi.org/10.1063/1.103279 (3 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
We have successfully synthesized single‐phase superconducting Y1−xCaxBa2Cu3Oy for 0≤x≤0.4 using a coprecipitation technique. All these compounds are orthorhombic with lattice parameters a∼3.83 and c varying from 11.69 to 11.67 Å. The Tc remains unchanged around 90 K. It may be noted that in these compounds Ca substitutes for Y. On the other hand, it is known that in the compounds where Ca substitutes for Ba, the structure changes to tetragonal and Tc decreases rapidly. [See G. J. Baldha, R. B. Jotania, H. H. Joshi, H. N. Pandya, and R. G. Kulkarni, Solid State Commun. 71, 839 (1989)]. Furthermore, these compositions sinter much better than pure 1:2:3 and one gets high‐density pellets (>95% of total density) at relatively lower temperature (<950 °C).
Show PACS
74.70.-b Superconducting materials other than cuprates
74.10.+v Occurrence, potential candidates
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
74.25.Sv Critical currents
74.62.Bf Effects of material synthesis, crystal structure, and chemical composition

Contact resistance of silver‐doped Y‐Ba‐Cu‐O in a magnetic field

S. Jin, J. E. Graebner, T. H. Tiefel, and G. W. Kammlott

Appl. Phys. Lett. 56, 186 (1990); http://dx.doi.org/10.1063/1.103280 (3 pages) | Cited 2 times

Full Text: | Download PDF

Show Abstract
The apparent contact resistance at the Ag‐particle/superconductor interface in sintered YBa2Cu3O7−δ is found to increase considerably in applied magnetic fields (e.g., by ∼300% at H=200 G, at 77 K). However, in a melt‐textured sample where the Ag particles are dispersed within the high Jc grain, no noticeable field dependence of ρc is obtained for H up to 1 T. The field dependence of apparent ρc in fine‐grained material is, therefore, attributed mostly to the local current concentration in the superconductor near the Ag particles. It causes Jc to be locally exceeded, with the voltage drop contributing to the apparent ρc value even though the average current density in the superconductor matrix is well below the Jc value. The importance of avoiding local current concentration by proper design and processing of silver contacts, and minimizing low Jc(H) region near the interface, is pointed out.
Show PACS
73.40.Cg Contact resistance, contact potential
74.25.Sv Critical currents
74.70.-b Superconducting materials other than cuprates

Multilayer YBa2Cu3Ox‐SrTiO3‐YBa2Cu3Ox films for insulating crossovers

John J. Kingston, Frederick C. Wellstood, Philippe Lerch, Andrew H. Miklich, and John Clarke

Appl. Phys. Lett. 56, 189 (1990); http://dx.doi.org/10.1063/1.103281 (3 pages) | Cited 49 times

Full Text: | Download PDF

Show Abstract
We describe our procedure for fabricating YBa2Cu3Ox‐SrTiO3‐YBa2Cu3Ox thin‐film trilayer structures. Each film is grown in situ by excimer laser deposition onto a heated (100)MgO substrate. The geometrical configuration of each layer is defined by a metal mask; the vacuum chamber is opened between depositions to allow the targets and masks to be changed. The lower and upper YBa2Cu3Ox films in the best trilayer structure had transition widths of 1 and 3 K (10–90%), respectively, and transition temperatures (zero resistance) of 87 K. The resistance between the YBa2Cu3Ox films at 77 K was 108 Ω for an overlapping area of 0.2 mm2, corresponding to a SrTiO3 resistivity of 4×109 Ω cm.
Show PACS
85.25.Qc Superconducting surface acoustic wave devices and other superconducting devices
74.78.-w Superconducting films and low-dimensional structures
74.70.-b Superconducting materials other than cuprates
85.40.Hp Lithography, masks and pattern transfer

Investigation of the ‘‘join’’ between the near edge and extended x‐ray absorption fine structure

F. W. Lytle and R. B. Greegor

Appl. Phys. Lett. 56, 192 (1990); http://dx.doi.org/10.1063/1.103282 (3 pages) | Cited 10 times

Full Text: | Download PDF

Show Abstract
The L1 and L3 x‐ray absorption fine structures from the same element in the same material were compared to illustrate the ‘‘join’’ between the x‐ray absorption near edge structure (XANES) and the extended x‐ray absorption fine structure (EXAFS). In the XANES region the two spectra differed because of the different selection rules; however, the EXAFS spectra were very similar when adjusted for the phase shift. For the oxide samples investigated the L1,3 spectra were similar for E>20 eV which identifies the demarcation between XANES and EXAFS.
Show PACS
78.70.Dm X-ray absorption spectra
07.85.-m X- and γ-ray instruments

Impact ionization mechanism in rare earth activated sulfides

K. Światek, A. Suchocki, and M. Godlewski

Appl. Phys. Lett. 56, 195 (1990); http://dx.doi.org/10.1063/1.103023 (3 pages) | Cited 20 times

Full Text: | Download PDF

Show Abstract
In this letter we present the theoretical estimation of the 3+☒2+ ionization energies of rare earth (RE) ions in sulfides. It is shown that for Yb, Eu, Sm, Tm, and Pr the RE2+ energy level is located in the forbidden gap of wide‐gap sulfides [ZnS (except Pr), CaS, SrS, BaS, MgS]. For these RE ions the possibility of a new efficient excitation mechanism (impact ionization) of electroluminescence is indicated. Highly efficient electroluminescence can be obtained if the ionized RE center rapidly recaptures a free carrier either directly or indirectly via the RE3+ excited state. This prediction is confirmed by the recent experimental results for Pr‐doped SrS. Further experimental results supporting the presented calculations are discussed.
Show PACS
79.20.Kz Other electron-impact emission phenomena
78.60.Fi Electroluminescence
71.55.Gs II-VI semiconductors

Low‐resistivity Cu thin‐film deposition by self‐ion bombardment

P. Bai, G.‐R. Yang, and T.‐M. Lu

Appl. Phys. Lett. 56, 198 (1990); http://dx.doi.org/10.1063/1.103024 (3 pages) | Cited 14 times

Full Text: | Download PDF

Show Abstract
An anomalous reduction of the thin‐film resistivity has been observed in the Cu deposition at room temperature using a partially ionized beam in which the self‐ions are used to bombard the substrate surface during growth. A minimum thin‐film resistivity of 1.83 μΩ cm has been obtained at 2 kV substrate bias voltage with an ion percentage of about 1% in the beam for films of 2500 Å thickness. This is compared to the resistivity of close to 4 μΩ cm obtained by the conventional evaporation technique without the use of self‐ions. We discuss the results within the framework of the theory of grain‐boundary resistivity proposed by Mayadas and Shatzkets [Phys. Rev. B 1, 1382 (1970)].
Show PACS
73.61.At Metal and metallic alloys
73.50.-h Electronic transport phenomena in thin films
81.40.Rs Electrical and magnetic properties related to treatment conditions
73.50.Bk General theory, scattering mechanisms
Page 2 of 2 Pages Previous Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close