Temperature Dependent Orientational Epitaxy of C60 Films on Noble Metal (111) Surfaces; Au, Ag and Cu

1994 ◽  
Vol 359 ◽  
Author(s):  
A. Fartash
Keyword(s):  
Noble Metal ◽  
Lattice Mismatch ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
Long Period ◽  
Molecular Beam Deposition ◽  
Unit Cells ◽  
Small Lattice ◽  
Substrate Temperatures ◽  
Lattice Matched

ABSTRACTHigh quality C60 films are grown on surfaces of (111) oriented noble metal substrates (i.e., Au, Ag, and Cu) by using a molecular beam deposition method. The structures of these films are compared with each other on substrates that are prepared to have similar in-plane mosaic widths (σ1.25*) as determined by their x-ray diffraction scans. The in-plane structures of these films are studied for substrate temperatures ranging from σ110 to 290°C. Although most materials grow in high symmetry small-lattice-mismatch in-plane orientations, C60 films (depending on their growth temperatures) grow in orientations that are poorly lattice matched with their Au(111) and Ag(111) substrates. In these orientations, C60 structures can be lattice matched only over large unit cells, forming “long-period ” structures. These “long-period ” structures coexist with “commensurate” structures that are almost perfectly lattice matched on twheitshe osur bpsrterdaotems.i naOten Au(111) substrates, a structural transition is observed between two distinct long-period structures (at Tc, σ150 °C). Although Au and Ag have similar lattice spacings, this transition is absent on Ag(111) substrates. The question of orientational epitaxy for C60 layers is examined in the context of several well-known systems in condensed matter physics.

Van der Waals Epitaxy of GaSe on GaAs(111)

1994 ◽  
Vol 340 ◽  
Author(s):  
L. E. Rumaner ◽  
F.S. Ohuchi
Keyword(s):  
Lattice Mismatch ◽  
Van Der Waals ◽  
Three Dimensional ◽  
Structured Materials ◽  
Lattice Matching ◽  
Molecular Beam Deposition ◽  
Crystal Films ◽  
Low Dimensional ◽  
Matching Constraints ◽  
Lattice Matched

ABSTRACTAlthough heteroepitaxy of lattice-matched and lattice-mismatched materials leading to artificially structured materials has resulted in impressive performance in various electronics devices, material combinations are usually limited by lattice matching constraints. A new concept for fabricating material systems using the atomically abrupt and low dimensional nature of layered materials, called van der Waals epitaxy (VDWE), has been developed. GaSe (Eg = 2.1 eV) has been deposited on the three dimensional surface of GaAs (111) using a molecular beam deposition system. GaSe was evaporated from a single Knudsen source, impinging on a heated substrate. Even with a lattice mismatch of 6% between the substrate and the growing film, good quality single crystal films were grown as determined by RHEED. The films have further been analyzed using a complementary combination of XPS and X-ray reflectivity.

Characterization of Epitaxial Fe on GaAs(110) by Scanning Tunneling Microscopy

1989 ◽  
Vol 151 ◽  
Author(s):  
R. A. Dragoset ◽  
P. N. First ◽  
Joseph A. Stroscio ◽  
D. T. Pierce ◽  
R. J. Celotta
Keyword(s):  
Scanning Tunneling Microscopy ◽  
Lattice Mismatch ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Small Lattice ◽  
Low Coverage ◽  
Substrate Temperatures ◽  
Stm Images ◽  
Interesting System

ABSTRACTIron on GaAs(110) comprises an interesting system not only due to small lattice mismatch, 1.4%, but also because of the magnetic properties of the overlayer. In the present work, scanning tunneling microscopy (STM) was used to investigate bcc Fe films in the 0.1 Å to 20 Å thickness range, grown at 300 K and 450 K substrate temperatures. STM images show Volmer-Weber growth with the formation of 3-D Fe islands 20–30 Å in diameter for 0.1–1 Å deposition at 300 K, increasing to 40–50 Å for thicker films. Iron island sizes at low coverage and thin film roughness at higher coverages both show significant dependence upon growth temperature.

Photoreflectance Characterization of InGaAs Lattice Matched to InP

1993 ◽  
Vol 324 ◽  
Author(s):  
V. Bellani ◽  
M. Amiotti ◽  
M. Geddo ◽  
G. Guizzetti ◽  
G. Landgren
Keyword(s):  
Energy Gap ◽  
Lattice Mismatch ◽  
Blue Shift ◽  
X Ray Diffraction ◽  
X Ray ◽  
Different Temperatures ◽  
Interfacial Strain ◽  
Valence Bands ◽  
Lattice Matched

AbstractWe measured photoreflectance (PR) spectra at different temperatures between 80 and 300 K, and optical absorption (OA) at 3 K on MOVPE grown Inl-xGaxAs nearly lattice-matched to InP. x-ray diffraction measurements gave a lattice mismatch δa/ao = -0.9.10−3 between ternary alloy and InP, corresponding to × = 0.485. We obtained the energy gap dependence on T from PR spectra. The blue shift of the gap was accounted for in terms of compositional difference with respect to the perfectly lattice matched alloy (× = 0.472), and elastic strain; moreover PR and OA showed evidence of the valence bands splitting at k = 0 due to interfacial strain, in fine agreement with theory.

Structure and mechanical properties of epitaxial TiN/V0.3Nb0.7N(100) superlattices

1994 ◽  
Vol 9 (6) ◽  
pp. 1456-1467 ◽  
Author(s):  
P.B. Mirkarimi ◽  
S.A. Barnett ◽  
K.M. Hubbard ◽  
T.R. Jervis ◽  
L. Hultman
Keyword(s):  
Elastic Modulus ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Crystalline Perfection ◽  
Composition Modulation ◽  
Superlattice Structure ◽  
Transmission Electron ◽  
Identical Composition ◽  
Coherency Strains ◽  
Lattice Matched

Epitaxial TiN/V0.3Nb0.7N superlattices with a 1.7% lattice mismatch between the layers were grown by reactive magnetron sputtering on MgO(001) substrates. Superlattice structure, crystalline perfection, composition modulation amplitudes, and coherency strains were studied using transmission electron microscopy and x-ray diffraction. Hardness H and elastic modulus were measured by nanoindentation. H increased rapidly with increasing Λ, peaking at H values ≍75% greater than rule-of-mixtures values at Λ ≍ 6 nm, before decreasing slightly with further increases in Λ. A comparison with previously studied lattice-matched TiN/V0.6Nb0.4N superlattices, which had nearly identical composition modulation amplitudes, showed a similar H variation, but a smaller H enhancement of ≍50%. The results suggest that coherency strains, which were larger for the mismatched TiN/V0.3Nb0.7N superlattices, were responsible for the larger hardness enhancement. The results are discussed in terms of coherency strain theories developed for spinodally decomposed materials. Nanoindenter elastic modulus results showed no significant anomalies.

On the substrate temperature dependence of the properties of In0.52Al0.48As/InP structures grown by molecular beam epitaxy

1996 ◽  
Vol 11 (9) ◽  
pp. 2158-2162 ◽  
Author(s):  
S.F. Yoon ◽  
Y. B. Miao ◽  
K. Radhakrishnan ◽  
S. Swaminathan
Keyword(s):  
Molecular Beam Epitaxy ◽  
Substrate Temperature ◽  
Molecular Beam ◽  
Lattice Mismatch ◽  
Strong Dependence ◽  
X Ray Diffraction ◽  
Lattice Constants ◽  
Wide Range ◽  
Energy Peak ◽  
Substrate Temperatures

Growth of In0.52Al0.48As epilayers on InP(100) substrates by molecular beam epitaxy at a wide range of substrate temperatures (470–550 °C) is carried out. Low temperature photoluminescence (PL) and double-axis x-ray diffraction (XRD) measurements showed a strong dependence of the PL and XRD linewidths and lattice mismatch on the substrate temperature. Minimum PL and XRD linewidths and lattice mismatch were found to occur at substrate temperatures of between ≈500 and 520 °C under the beam fluxes used in this study. The XRD intensity ratios (Iepi/Isub) were generally higher within the same substrate temperature range at which the lattice mismatch was the lowest. XRD rocking curves of samples grown at low temperatures showed the main epilayer peak to be composed of smaller discrete peaks, suggesting the presence of regions with different lattice constants in the material. PL spectra taken at increasing temperatures showed the quenching of the main emission peak followed by the evolution of a distinct lower energy peak which is possibly associated with deep lying centers.

Structural Properties Studies of GaN on 6H-SiC by Means of X-Ray Diffraction Technique

2010 ◽  
Vol 173 ◽  
pp. 40-43
Author(s):  
Ching Chin Guan ◽  
Sha Shiong Ng ◽  
Hassan Zainuriah ◽  
Abu Hassan Haslan
Keyword(s):  
Structural Properties ◽  
Lattice Mismatch ◽  
Hexagonal Lattice ◽  
Laser Cavity ◽  
Device Fabrication ◽  
X Ray Diffraction ◽  
Wurtzite Phase ◽  
Light Emitting ◽  
X Ray ◽  
Small Lattice

Epitaxial growth of GaN has become an interest topic in term of light emitting device fabrication. Most of the commercial GaN based device is normally grown on sapphire substrate. For power device application, SiC has been found to be a desirable candidate for GaN epilayer due to their high thermal conductivity, small lattice mismatch, and hexagonal lattice mismatch with cleaved facet for the laser cavity. In this paper, X-ray diffraction (XRD) technique is employed to study the structural properties of GaN thin film grown on 6H-SiC substrate. For conventional XRD -2 scan, only diffraction peaks from GaN (002) and its multiple diffractions were observed, along with diffractions from SiC (006) peak. These results suggested that the GaN film is in wurtzite phase. For XRD rocking curve of omega scan of (002) diffraction plane of the GaN, a full width at half maximum of about 259 arcsec is obtained.

Thermal Expansion Behavior of ZnSe and ZnS0.03Se0.97 Epilayers on GaAs at Temperatures in the Range, 25°C - 250°C

1994 ◽  
Vol 340 ◽  
Author(s):  
J. R. Kim ◽  
R. M. Park ◽  
K. S. Jones
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Lattice Mismatch ◽  
X Ray Diffraction ◽  
Thermal Expansion Behavior ◽  
Lattice Constants ◽  
Thermal Expansion Coefficients ◽  
Expansion Behavior ◽  
Expansion Coefficients ◽  
Lattice Matched

ABSTRACTThe thermal expansion behavior of ZnSe and ZnS0.03Se0.97 epilayers grown on GaAs has been investigated using high resolution X-ray diffraction at temperatures between room temperature and the growth temperature. The lattice parameters perpendicular and parallel to the surface were measured with the Bond's method. The lattice mismatch for a partially relaxed ZnSe layer was Δa(⊥)/a =2300 ppm and Δa(‖)/a = 2600 ppm at room temperature(R.T.) and Δa (⊥)/a =3600 ppm and Δa(‖)/a =2400 ppm at 250°C. For ZnS0.03Se0.97 which is almost lattice matched at R.T. to GaAs, Δa(⊥)/a =200 ppm, Δa(⊥)/a =20ppmatR.T. and Δa(⊥)/a =1400ppm, Δa(⊥)/a =50ppm at 250°C. The relaxed lattice constants were evaluated and the thermal expansion coefficients of relaxed ZnSe layers were found to vary from 7.8*10−6/°C at room temperature to 12.2*10−6/°C at 250°C and for ZnS0.03Se0.97 layers the variation was from 7.5*10−6/°C at R.T. to 11.7*10−6/°C at 250°C.

Initial Stages of Gaas Growth on Scl-XErxas Surfaces

1990 ◽  
Vol 202 ◽  
Author(s):  
Terje G Finstad ◽  
C. J. Palmstrøm ◽  
S. Mounier ◽  
V. G. Keramidas ◽  
J. G. Zhu ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Substrate Temperature ◽  
Lattice Mismatch ◽  
High Energy ◽  
Energy Electron ◽  
Interference Microscopy ◽  
Strong Tendency ◽  
Moderate Growth ◽  
Substrate Temperatures ◽  
Lattice Matched

ABSTRACTLattice matched ScxEr1-xAs (ScErAs) was grown on GaAs by MBE followed by a GaAs overlayer. The overgrowth of GaAs on ScErAs has been studied by Reflection High Energy Electron Diffraction (RHEED), Low Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES), Nomarskii-interference microscopy and Transmission Electron Microscopy (TEM). In this study substrate temperature and crystal orientation have been varied. For GaAs growth on (100)ScErAs there is a strong tendency for island formation and three dimensional (3D) growth. For high substrate temperatures (>500 °C) and for moderate growth rates (10 ML/min) the growth can be described by the Volmer-Weber mode. For lower substrate temperatures we observe that one monolayer of GaAs on ScErAs is metastable. This monolayer shows a (3×1)/(1×3) surface reconstruction. The deposition of more than one monolayer, irrespective of substrate temperature, or the raising of the substrate temperature induces island growth. The metastable reconstructed surface layer of GaAs then partly dissolves into the islands. The strong tendency for 3D growth observed here is very similar to that seen in the growth on ErAs which is not lattice matched to GaAs. This observation demonstrates the significance of electronic bonding mismatch over lattice mismatch for heteroepitaxy between materials with ionic and covalent bonding character. Growth on {111}-polar surfaces yields smoother layers and a stronger tendency for 2D growth.

TEM study of Cosi2 formation via annealing of Co-Ti bilayers on Si

1995 ◽  
Vol 53 ◽  
pp. 464-465
Author(s):  
N. David Theodore ◽  
Andre Vantomme ◽  
Peter Crazier
Keyword(s):  
Thermal Instability ◽  
Lattice Mismatch ◽  
Field Effect Transistors ◽  
Contact Layer ◽  
Interface Roughness ◽  
Oxide Semiconductor ◽  
Surface Layers ◽  
Silicide Layer ◽  
Small Lattice ◽  
Buried Layers

Contact is typically made to source/drain regions of metal-oxide-semiconductor field-effect transistors (MOSFETs) by use of TiSi2 or CoSi2 layers followed by AI(Cu) metal lines. A silicide layer is used to reduce contact resistance. TiSi2 or CoSi2 are chosen for the contact layer because these silicides have low resistivities (~12-15 μΩ-cm for TiSi2 in the C54 phase, and ~10-15 μΩ-cm for CoSi2). CoSi2 has other desirable properties, such as being thermally stable up to >1000°C for surface layers and >1100°C for buried layers, and having a small lattice mismatch with silicon, -1.2% at room temperature. During CoSi2 growth, Co is the diffusing species. Electrode shorts and voids which can arise if Si is the diffusing species are therefore avoided. However, problems can arise due to silicide-Si interface roughness (leading to nonuniformity in film resistance) and thermal instability of the resistance upon further high temperature annealing. These problems can be avoided if the CoSi2 can be grown epitaxially on silicon.

Time Dependence of γ/γ' Lattice Mismatch in Creep-Deformed Single Crystal Superalloy SC16 at 1173 K

2007 ◽  
Vol 539-543 ◽  
pp. 3059-3063 ◽  
Author(s):  
G. Schumacher ◽  
N. Darowski ◽  
I. Zizak ◽  
Hellmuth Klingelhöffer ◽  
W. Chen ◽  
...  
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
Lattice Misfit ◽  
Peak Position ◽  
Single Crystal Superalloy ◽  
Tensile Creep ◽  
Full Width ◽  
X Ray Diffraction ◽  
X Ray ◽  
Time Period

The profiles of 001 and 002 reflections have been measured at 1173 K as a function of time by means of X-ray diffraction (XRD) on tensile-creep deformed specimens of single crystal superalloy SC16. Decrease in line width (full width at half maximum: FWHM) by about 7 % and increase in peak position by about 3x10-4 degrees was detected after 8.5x104 s. Broadening of the 002 peak profile indicated a more negative value of the lattice misfit after the same time period. The results are discussed in the context of the anisotropic arrangement of dislocations at the γ/γ’ interfaces during creep and their rearrangement during the thermal treatment at 1173 K.

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