摘要:

Zn1−xMgxSe alloys have been grown on (100) GaAs substrates by molecular beam epitaxy. Their crystal structures are determined form x‐ray diffraction spectra and are found to be zinc blende, rocksalt, and their mixture forx<0.5,x=1, andx∼0.6, respectively. The Raman spectra are measured and show two‐mode behavior for those alloys with zinc blende structure. The long‐wavelength frequencies of ZnSe‐ and MgSe‐like optical phonons are determined and the results can be expressed as linear functions ofx. The first‐order Raman spectra are observed for MgSe and Mg‐rich Zn1−xMgxSe alloys with rocksalt structure. Those Raman spectra are attributed to the scattering from optical phonons activated by disorders and impurities, and their line shapes represent the phonon density of states. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115334

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Wafer bonding of commercial 4 in. silicon wafers has been performed at room temperature under ultrahigh vacuum conditions. After local initiation of the bonding process the bonding area is self‐propagating just as in the case of wafer bonding under atmospheric conditions. The room‐temperature bonded wafers, without any additional heat treatment show a bonding strength typical for bulk material. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115335

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Spontaneously formed long‐range Al‐rich and Ga‐rich AlxGa1−xAs/AlyGa1−yAs superlattice in (111)A was demonstrated. This was observed by cross‐sectional transmission electron microscopy (TEM) in 0.75 &mgr;m Al0.30Ga0.70As grown on (111)A GaAs substrates at 640 °C. In contrast, none of the above superstructure was observed by TEM on a side‐by‐side grown (100) oriented substrate. 15 K photoluminescence (PL) showed a 31 meV redshift and six times peak intensity enhancement in layers grown on (111)A substrates to that on (100). A reduced long‐range compositional modulation can be achieved by growth at higher temperatures and is shown in the finer and moderately modulating (111)A Al0.40Ga0.60As grown at 700 °C. A 15 K PL linewidth of 17 meV was achieved in 700 °C grown (111)A A0.40Ga0.60As that is the narrowest reported linewidth for (111)A AlGaAs. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115336

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A deuterated Si(111) surface has been fabricated by wetting in deionized hot heavy water without oxidizing the surface. The surface had a single dominant absorption feature with a narrow width in the infrared spectrum. The surface was mainly composed of monodeuterides whose Si–D bonds are normal to the surface, and partially of other deuteride structures. The surface structure was quite similar to H/Si(111) formed in hot water. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115337

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We deposit polycrystalline silicon (px‐Si) with mean grain diameter ∼400 A˚ using dc magnetron sputtering of a Si target in an Ar plasma. We analyze the nucleation process and crystallite size as a function of film thickness usinginsitu, real time spectroscopic ellipsometry. For direct deposition on glass substrates at 470 °C, the initial ∼0.3 &mgr;m is amorphous silicon, then crystalline nuclei appear, and the growth becomes fully polycrystalline by ∼0.6 &mgr;m. To promote nucleation, we deposit a 100 A˚ layer of &mgr;c‐Si:H (hydrogenated polycrystalline silicon with a mean grain diameter of ∼60 A˚) by sputtering in an Ar plus H2atmosphere at 210 °C. Returning to an Ar‐only plasma at 470 °C, px‐Si grows on this seeded substrate with no detectable amorphous interfacial layer. Since magnetron sputtering is a large‐area, high throughput technique, this two‐step process appears technologically attractive. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115338

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Ga0.5ln0.5P layers grown by organometallic vapor phase epitaxy at rates of between 0.1 and 4.0 &mgr;m/h on exactly (001)‐oriented GaAs substrates have been studied using atomic force microscopy. The surface is found to be covered by islands several monolayers in height that are elongated in the [110] direction. The edges of the islands are formed of clearly resolved bilayer (5.9 A˚) steps. Monolayer steps are rare and no steps larger than 6 A˚ were observed. These observations explain the nature of the order twin boundaries in ordered GaInP grown on exactly (001)‐oriented substrates. The (001) domain laminae are always found to consist of an even number of monolayers. For bilayer steps, the domain thickness will be twice the number of steps moving across the surface before the direction of step motion switches due to the undulating nature of the surface. This switch in the direction of step motion at a particular location on the surface produces the order twin boundaries observed. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.115339

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The temperature dependence of photoluminescence (PL) properties of AlGaAs/GaAs quantum wire (QWR) grown on V‐grooved substrates by flow rate modulation epitaxy is investigated. PL from a 7.1 nm thick QWR is easily observed even at room temperature. The full width at half‐maximum (FWHM) of the QWR emission peak increases linearly with increasing temperature at low temperatures and becomes almost independent of temperature at high temperatures, while that of a quantum well layer (QWL) sample increases with increasing temperature up to room temperature. The FWHM of QWR is found to be considerably narrower than that of the QWL sample at high temperatures, which is expected theoretically from the sharp one‐dimensional density of states of QWR but has not been clearly observed experimentally. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115340

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A comparison between compositionally stepped and alternating step‐graded structures used in the production of a relaxation buffer layer is carried out by means of transmission electron microscopy. The latter shows higher efficiency in relieving the strain. A simple balance force model permits us to understand the reason for a higher generation of threading dislocations observed in the alternating step‐graded structures. The presented results can be applied as new design rules for buffer fabrication that contrast in some key points with previous published rules as, for example, the ‘‘zero‐net‐strain’’ precept [D. Dunstan, P. Kidd, P. F. Fewster, N. L. Andrew, L. Gonza´lez, Y. Gonza´lez, A. Sacedo´n, and F. Gonza´lez‐Sanz, Appl. Phys. Lett.65, 845 (1994)]. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115341

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The atomic structure of the interfaces of Josephson junctions formed by epitaxial YBa2Cu3O7/PrBa2Cu3O7/YBa2Cu3O7triple‐layer films was investigated by high‐resolution transmission electron microscopy. The samples were fabricated by sputter deposition on surfaces which were etchedexsitueither chemically, using a nonaqueous Br‐ethanol solution, or by an Ar ion beam. In the interfaces produced after ion etching a thin intermediate layer with a thickness of a few nanometers was observed. The main part of this layer consists of cubic PrBa2Cu3O7or YBa2Cu3O7which is cation disordered. The interfaces formed during deposition on Br‐ethanol‐etched surfaces did not contain such an intermediate layer but exhibited high structural perfection similar to that of interfaces producedinsitu. These observations permit a qualitative explanation of the difference in the electrical properties of junctions produced by these two techniques. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115342

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Sputter deposited MgO thin films with the B1 crystal structure and (002) film texture are used as seed layers to improve the texture and magnetic properties of the CoCrPt/Cr magnetic thin films on glass substrates for longitudinal recording. The desired (002) textured Cr underlayers are usually obtained by sputtering Cr onto heated substrates. However, it is found that the MgO seed layers can induce the (002) film texture in the Cr underlayers without using a heated substrate and hence, the overlying CoCrPt films are formed with the (112¯0) texture. Vibrating‐sample magnetometry measurements show greatly improved in‐plane coercivities that are suitable for future high density recording media can be easily obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115343

出版商:AIP    

年代:1995

数据来源: AIP