摘要:

The infrared response of polycrystalline and epitaxial CoSi2/Si Schottky diodes with similar silicide thickness has been measured. For the polycrystalline diodes the quantum efficiency is found to be two times higher than for the epitaxial diodes, although both types of diodes present very similar barrier height. The observed improvement is attributed to grain boundary scattering of the excited carriers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115537

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have developed an atomic monitoring system for physical vapor deposition process control based on a frequency‐modulation (FM) spectroscopy scheme using a 670 nm external cavity diode laser. FM detection made it possible to measure absorption as low as 10−6. For electron‐beam evaporated yttrium, deposition rate control with a relative accuracy better than 1% at a rate of 3.5 A˚/s has been realized, corresponding to a deposition rate resolution of 0.03 A˚/s. Variations in Doppler shifts due to the velocity distribution of the atomic vapor within the deposition chamber have been measured, demonstrating the possibility of velocity mapping of evaporated atoms in the deposition process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115538

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Fabrication of a two‐dimensional array of nanometer‐scale chromium features on a silicon substrate by laser‐focused atomic deposition is described. Features 13±1 nm high and having a full‐width at half maximum of 80±10 nm are fabricated in a square array with lattice constant 212.78 nm, determined by the laser wavelength. The array covers an area of approximately 100 &mgr;m×200 &mgr;m. Issues associated with laser‐focusing of atoms in a two‐dimensional standing wave are discussed, and potential applications and improvements of the process are mentioned.

ISSN:0003-6951    

DOI:10.1063/1.115539

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Characterization of bulk single crystals and optical waveguides in Ba1−xSrxTiyNb2−yO6(BSTN) indicate it to be a promising new ferroelectric material for electrooptic devices. The electro‐optic coefficientr33is measured to be 218±12 pm/V, a factor of 7 greater than LiNbO3. Data on refractive indices, dielectric constant, and Curie temperatureTcin bulk samples are also presented. Strain‐induced waveguides inZ‐cut samples exhibited low losses (1.8 dB/cm for TM polarization and 2.5 dB/cm for TE polarization) at a wavelength of 1.3 &mgr;m. Electro‐optic modulation was demonstrated in these waveguides to frequencies ≳100 MHz. A ‘‘self‐poling’’ effect was found, whereby strong electro‐optic modulation is observed in the strain waveguides without repoling the crystal after processing at temperatures far aboveTc. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115540

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new organometallic source, tritertiarybutylaluminum (TTBAl), has been used in growth of AlxGa1−xSb epilayers by low pressure organometallic vapor phase epitaxy. Ternary alloys were grown over the whole composition range 0<x≤1 on GaSb and GaAs substrates from TTBAl, triethylgallium, and triethylantimony (TESb) or trimethylantimony (TMSb). All layers exhibited mirror surface morphologies. Photoluminescence was observed for layers withx<0.2, the composition that corresponds to the indirect transition. The background of C and O in AlSb grown with TESb was ∼2×1018and ∼6×1019cm−3, respectively, and ∼1.5×1019and ∼1.5×1019cm−3, respectively, for AlSb grown with TMSb. All layers exhibitedp‐type conductivity with hole concentration increasing withx, and saturating ∼5×1018cm−3forx=1, which is about 10 times lower compared to layers grown with conventional Al sources. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115541

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the growth and characterization of epitaxial Ba0.5Sr0.5TiO3/SrRuO3/ZrO2on Si for potential charge storage applications. Both Ba0.5Sr0.5TiO3(BST) and SrRuO3(SRO) are grown (110)‐oriented on yttrium‐stabilized ZrO2(YSZ) (100)‐buffered Si. These films show a high degree of crystallinity with minimal interdiffusion at the interfaces as evidenced from x‐ray diffraction, Rutherford backscattering, and transmission electron microscopy. Studies on the in‐plane crystallographic relations between the layers revealed an interesting rectangle‐on‐cube epitaxy between BST/SRO and YSZ. The dielectric constant and loss tangent of the BST dielectric layer are 360 and 0.01 at 10 kHz, respectively. The leakage current density is lower than 4×10−7A/cm2at 1 V. A strong frequency dependence on both dielectric constant and loss tangent is observed in 1–10 MHz frequency range. This is attributed to the effect of a series resistance in the measurement loop, which is likely related to the bottom SrRuO3electrode. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115542

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have grown epitaxial ZnSe films on (001)GaAs substrates at 300 °C by pulsed laser deposition (PLD). Before the growth, thin buffer layers of GaAs are also grown by PLD at 300 °C. While the pattern of reflection high energy electron diffraction (RHEED) of the buffer layers is spotty, the pattern of the ZnSe films subsequently grown is streaky, and shows distinct Kikuchi lines and bands. The x‐ray rocking curve width of the films is as narrow as 150 arcsec. Photoluminescence (PL) at 10 K of the films shows free and bound excitons, donor‐acceptor pairs (DAP), and is free of any deep level emissions, indicating good crystalline quality of the films. Scanning electron microscopy (SEM) shows that the particulate number density of the films is only about 1 particulate per 400 &mgr;m2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115543

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Strained In0.21Ga0.79As/GaAs quantum well structures have been grown by molecular beam epitaxy on (111)B GaAs substrates. Well widths between 20 and 160 A˚, separated by 500 A˚ barriers were grown sequentially on the same substrate and subsequently characterized by low‐temperature (10 K) photoluminescence. The variation of thee‐hh transition energy with well width is markedly different for samples grown simultaneously on (100) and (111)B substrates due to the strain induced piezoelectric field. Using the envelope function approximation, the dependence ofn=1e‐hh transitions of (111)B samples on well width can be interpreted by the presence of a built‐in electric field of magnitude of 1.45×107V/m. In contrast to the (100) sample, exciton lifetimes in the (111)B sample depend strongly on well width because of spatial separation of electrons and holes in the triangular wells. In the 160 A˚ well, the exciton lifetime increases to 755 ns corresponding to a reduction of about three orders of magnitude in the electron‐hole wave function overlap integral. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115544

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The role of Si dangling bonds (Pbcenter) on the broad luminescence band around 1.1 eV of porous Si is discussed, based on transient wave form measurement of optically detected magnetic resonance. The observed wave form is compatible with the nongeminate shunt path scheme and the characteristic time constant of this nonradiative process is deduced to be 15 &mgr;s at 1.6 K, whereas the competing radiative channel has a shorter decay time of 3 &mgr;s. Therefore,Pbcenters are unlikely to be involved as a radiative state in this infrared luminescence. Results are also discussed in conjunction with the visible luminescence process. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114505

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The influence of supplemental O+implantation on standard separation‐by‐implantation of oxygen (SIMOX) structures in terms of inherent defects has been analyzed by electron spin resonance. The monitored defects include theE&ggr;′andE&dgr;′variants of the oxygen‐deficiency centers in the buried oxide layer (BOX), and the likely O‐related, shallow donor (UL1) centers in buried interfacial Si layers.E′ generation sensitivity depth profiles were mapped using etch back in combination withE′ generation by exposure to a dc Ar glow discharge. A major finding is that supplemental O implantation significantly reduces theE′ generation sensitivity (precursor sites) quite uniformly all over the BOX layer. The reduction, though, is about two times greater forE&dgr;′as compared toE&ggr;′. The UL1 centers, by contrast, are seen to increase by up to a factor 6. Apparently these defects, inherent to the SIMOX formation process, are insufficiently removed by the postsupplemental O+implantation anneal performed at 1100 °C. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114506

出版商:AIP    

年代:1995

数据来源: AIP