C. Scheck

Selective metal electrodeposition through doping modulation of semiconductor surfaces

We demonstrate selective electrodeposition of magnetic layers on doped semiconductors resulting in a self-aligned pattern which replicates the doping pattern in the semiconductor surface. A Schottky barrier forms at the interface between a semiconductor substrate and the electrolyte, which upon application of a cathodic potential is biased in the forward (reverse) direction for n- or p-type semiconductors, respectively. Electron transfer from an n-type semiconductor is thus possible, while breakdown of the Schottky barrier would be necessary for deposition on a p-type substrate. The process will thus be spatially selective on a lateral modulation of the substrate doping. As an example we demonstrate the deposition of Co on GaAs.

Sharp ferromagnet/semiconductor interfaces by electrodeposition of Ni thin films onto n-GaAs(001) substrates

We report on the chemical, electrical, and magnetic properties of Ni/GaAs(001) interfaces prepared using electrodeposition. Electrodeposition is an equilibrium process which thus releases much less energy per absorbed atom than other deposition techniques. This allows preparation of chemically sharp interfaces which otherwise show a high degree of reactivity and interdiffusion. This is demonstrated by the example of Ni grown on GaAs(001). Photoelectron spectroscopy shows the absence of surface segregation of substrate material or diffusion into the Ni layer. This is confirmed by the electrical and magnetic properties of the films.

Structure and magnetic properties of electrodeposited Ni films on n-GaAs(001)

We report the structural and magnetic properties of Ni films grown on GaAs(001) using electrodeposition, covering the thickness range 0–80 nm. The structure is characterized by mixed (001) and (011) epitaxial orientation of fcc Ni with a preference for the Ni(001) orientation. The magnetic anisotropy is originated by a combination of a crystalline contribution with fourfold symmetry and a uniaxial anisotropy probably caused by the asymmetry in the substrate surface structure. The saturation magnetic moment varies linearly with thickness, indicating limited intermixing between Ni film and GaAs substrate. This is ascribed to the low-energy deposition process characteristic of electrodeposition.

Epitaxial Growth of Fe Films on n-Type GaAs by Electrodeposition

We report epitaxial growth of Fe thin films on both n-type GaAs(001) and GaAs(011) substrates using electrochemical deposition. The structural quality depends on the composition of the plating solution. The magnetic properties are characterized by fourfold crystalline anisotropy for the Fe(001) film while for the Fe(011) layers we observe a uniaxial anisotropy induced by the substrate asymmetry. The in-plane coercivity is around 30-100 Oe.

Evolution of interface properties of electrodeposited Ni/GaAs(001) contacts upon annealing

We demonstrate how epitaxial FM (Ni) films can be grown by ECD directly onto GaAs(001) without outdiffusion or surface segregation of As or Ga. The thickness dependence of electrical and magnetic properties (saturation magnetic moment) verify the good quality of the layers and indicate that electrochemical deposition is a suitable candidate for the growth of epitaxial Ni films with sharp interfaces on GaAs(001). X-ray photoelectron spectroscopy (XPS) analysis on electroplated (epitaxial) Ni films showed no interdiffusion for annealing up to 250 °C. Annealing at higher temperatures, up to 350 °C, significantly increases both the As outdiffusion and the Schottky barrier heights, which indicates the correlation between intermixing and the diode quality.

Thickness dependence of magnetic anisotropy in thin Ni films electrodeposited onto the (011) and (001) surfaces of n-GaAs

Brillouin light scattering from thermal spin waves has been exploited to investigate the thickness dependence of magnetic anisotropy of Ni films, with thickness in the range 7–35nm, grown by electrodeposition onto either (011)- or (001)-GaAs substrates. In the former case, Ni films exhibit a well-defined in-plane uniaxial anisotropy induced by the symmetry of the substrate. In the case of the (001)-GaAs substrate, instead, the magnetic anisotropy results from a combination of both a fourfold and a twofold contribution. The physical mechanisms responsible for the observed anisotropy, as well as its dependence on film thickness, are discussed in detail.

Photoexcited electrodeposition of Cu structures on p-Si(001)

Selective growth of metals on semiconductors has recently raised considerable interest due to its possible application in the direct formation of conduction paths and contacts on semiconductors. We produced small structures by photoexcited electroless plating of Cu on p-type Si(001). The p-type substrate forms a Schottky barrier with the solution which inhibits the plating process. Local illumination creates minority carriers which become available to discharge metal ions. Illumination was done by converging a 1–5 mW laser beam to a 1–2 μm focus diameter on the substrate in the plating solution using an optical microscope. The dimensions of the dots are determined by the diffusion length of the excited minority carriers. We analyzed the diameter of the growing dots as a function of the laser light wavelength and intensity, illumination duration, composition of the solution and charge carrier lifetime in the substrate. The lateral dimensions of the structures produced are found to decrease with reduced las...

Epitaxial growth and magnetic anisotropy of electrodeposited Ni and Co thin films grown on n-type GaAs

Summary form only given. Ferromagnetic films on semiconductors can be used in the fabrication of magnetic sensors, memories, and novel devices based on spin-dependent transport phenomena. Electrochemical deposition offers some advantages with respect to UHV techniques for the growth of these structures, such as the low temperature processing, which can limit the interdiffusion between the film and substrate, thus creating well defined interfaces. We have studied the electrochemical growth and magnetic anisotropy of Ni and Co on [001]- and [011]-oriented n-GaAs.

Anisotropy of epitaxial Fe films grown on n-type GaAs by electrodeposition

We report the epitaxial growth of high quality Fe thin films on both n-type GaAs(001) and GaAs(011) substrates using electrochemical deposition. X-ray diffraction shows Fe(001)[110]//GaAs(001)[110] and Fe(011)[100]//GaAs(011)[100] as the primary epitaxial relations similarly to Fe films grown by molecular-beam epitaxy. The structural quality depends on the composition of the plating solution. The Hc values of these films are around 30–100 Oe. The 4πMs value is about 20–21 kG. In-plane angular ferromagnetic resonance measurements showed crystalline anisotropy for both the Fe(001) and Fe(011) films which is superimposed by a substrate induced uniaxial anisotropy for the Fe(011) layers.

Electrodeposition as a Versatile Analytical and Preparation Tool

a MINT Center and Dept. of Physics, U. of Alabama, Tuscaloosa AL 35487, USA b Department of Materials Science and Engineering, Columbia University, New York, NY 10027, USA c ELMOS Semiconductor AG, Heinrich-Hertz-Str. 1, 44227 Dortmund, Germany d Department of Materials Science & Engineering, and Center for Electrochemical Science & Engineering, University of Virginia, Charlottesville, VA 22904, USA.