http://experimentationlab.berkeley.edu/sites/default/files/AFMImages/butt_AFM.pdf

Force measurements with the atomic force microscope: Technique, interpretation and applications

Physical Review B

The fabrication methods of the microelectronics industry have been refined to produce ever smaller devices, but will soon reach their fundamental limits. A promising alternative route to even smaller functional systems with nanometre dimensions is the autonomous ordering and assembly of atoms and molecules on atomically well-defined surfaces. This approach combines ease of fabrication with exquisite control over the shape, composition and mesoscale organization of the surface structures formed. Once the mechanisms controlling the self-ordering phenomena are fully understood, the self-assembly and growth processes can be steered to create a wide range of surface nanostructures from metallic, semiconducting and molecular materials.

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Engineering atomic and molecular nanostructures at surfaces

1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.

Thin Film Materials: Stress, Defect Formation and Surface Evolution

On the basis of different types of experiments, the authors develop implicitly the model of surface-enhanced Raman scattering (SERS) of adsorbates on metal surfaces. The long-range enhancement by resonances of the macroscopic laser and Stokes field is separated quantitatively from the metal electron-mediated resonance Raman effect. The latter mechanism proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to orbitals of the adsorbates. This model can account for the chemical specificity and vibrational selectivity of SERS and (partly) for the SERS specificity of the various metals.

https://iopscience.iop.org/article/10.1088/0953-8984/4/5/001/pdf

Surface-enhanced Raman scattering

Growth and characterization of epitaxial Ni and Co silicides

We have investigated the epitaxial growth and the electronic properties of a metallic metastable FeSi phase crystallizing with the CsCl structure on Si(111) Upon annealing below 500 \ifmmode^\circ\else\textdegree\fi{}C the stoichiometry of thin films (20 \AA{}) evolves towards ${\mathrm{FeSi}}_{2}$ with no change of symmetry, ie, the defect CsCl structure with a statistical occupation of metal sites remains epitaxially stable for all ${\mathrm{FeSi}}_{1+\mathit{x}}$ (0\ensuremath{\le}x\ensuremath{\le}1) Films thicker than -20 \AA{} exhibit a transition to the cubic \ensuremath{\epsilon}-FeSi phase The electronic band structure of FeSi (CsCl) has been calculated self-consistently using the full-potential linear augmented--plane-wave method

Structural and electronic properties of metastable epitaxial FeSi1+x films on Si(111).

We review the potential of low-energy plasma-enhanced chemical vapor deposition (LEPECVD) for the fabrication of strained Si and Ge heterostructures and devices. The technique is shown to be equally applicable to the formation of relaxed SiGe buffer layers, and to entire heterostructures including strained modulation doped channels. Pure Ge channels on Ge-rich linearly graded buffers are shown to exhibit low-temperature hole mobilities up to 120,000 cm 2 V � 1 s � 1 , limited by remote impurity and background impurity scattering rather than interface roughness scattering. Strained-Si modulation-doped field-effect transistors (n-MODFETs) with excellent frequency response have been fabricated by combining LEPECVD and MBE for buffer layer and active layer growth, respectively. Maximum oscillation frequencies of n-MODFETs above 140 GHz have been achieved for active layer stacks both on buffers linearly graded to a Ge fraction of 40% at a rate of 10% per micron, and on constant composition buffers which are 10 times thinner. The use of a thin buffer results in significantly less device self-heating. � 2004 Elsevier Ltd. All rights reserved.

Low-energy plasma-enhanced chemical vapor deposition for strained Si and Ge heterostructures and devices

The evolution of strained Ge $/$Si(001) islands during exposure to a Si flux was investigated by scanning tunneling microscopy. Dome islands display appreciable shape changes at Si coverages as low as 0.5 monolayer. With increasing coverage, they transform into ${105}$-faceted pyramids, and eventually into stepped mounds with steps parallel to the $〈110〉$ directions. These morphological changes are induced by alloying and represent a complete reversal of those previously observed during Ge island growth. The results are interpreted with a simple model in which the equilibrium shape of an island mainly depends on its volume and composition.

Reversible shape evolution of Ge islands on Si(001).

A new technique for semiconductor epitaxy at low substrate temperatures is presented, called low-energy dc plasma enhanced chemical vapor deposition. The method has been applied to Si homoepitaxy at substrate temperatures between 400 and 600 °C and growth rates between 0.1 and 1 nm/s, using silane as the reactive gas. The quality of the Si films has been examined by reflection high-energy electron diffraction, scanning tunneling microscopy, cross-section transmission electron microscopy, and high-resolution x-ray diffraction. Two effects have been identified to lead to the formation of stacking faults after an initial layer of defect-free growth: (1) substrate bombardment by ions with energies in excess of 15 eV, and (2) hydrogen adsorption limiting the surface mobility of Si atoms and silane radicals. Both result in the accumulation of surface roughness, facilitating the nucleation of stacking faults when the roughness reaches a critical level. Defect introduction can be eliminated effectively by biasing the substrate during growth and by decreasing the hydrogen coverage, either by admixing small amounts of germane to the silane or by using a sufficiently high plasma density.

H. von Känel

Papers

Growth and characterization of epitaxial Ni and Co silicides

Structural and electronic properties of metastable epitaxial FeSi1+x films on Si(111).

Low-energy plasma-enhanced chemical vapor deposition for strained Si and Ge heterostructures and devices

Reversible shape evolution of Ge islands on Si(001).

Silicon epitaxy by low-energy plasma enhanced chemical vapor deposition