Single-atom doping for quantum device development in diamond and silicon

The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in single atoms, such as proposed quantum computers. We describe a single atom injector, in which the imaging and alignment capabilities of a scanning force microscope (SFM) are integrated with ion beams from a series of ion sources and with sensitive detection of current transients induced by incident ions. Ion beams are collimated by a small hole in the SFM tip and current changes induced by single ion impacts in transistor channels enable reliable detection of single ion hits. We discuss resolution limiting factors in ion placement and processing and paths to single atom (and color center) array formation for systematic testing of quantum computer architectures in silicon and diamond

Electron-correlation effects in appearance-potential spectra of Ni

Spin-resolved and temperature-dependent appearance-potential spectra of ferromagnetic Nickel are measured and analyzed theoretically. The Lander self-convolution model which relates the line shape to the unoccupied part of the local density of states turns out to be insufficient. Electron correlations and orbitally resolved transition-matrix elements are shown to be essential for a quantitative agreement between experiment and theory.Comment: LaTeX, 6 pages, 2 eps figures included, Phys. Rev. B (in press

DMCMN: In Depth Characterization and Control of AFM Cantilevers With Integrated Sensing and Actuation

New developments in MEMS (microelectromechanical systems) fabrication allowed the development of new types of atomic force microscopy (AFM) sensor with integrated readout circuit and actuator built in on the cantilever. Such a fully instrumented cantilever allows a much more direct measurement and actuation of the cantilever motion and interaction with the sample. This technology is expected to not only allow for high speed imaging but also the miniaturization of AFMs. Based on the complexity of these integrated MEMS devices, a thorough understanding of their behavior and a specialized controls approach is needed to make the most use out of this new technology. In this paper we investigate the intrinsic properties of such MEMS cantilevers and develop a combined approach for sensing and control, optimized for high speed detection and actuation. Further developments based on the results presented in this paper will help to expand the use of atomic force microscopy to a broad range of everyday applications in industrial process control and clinical diagnostics

GaAs FET characterization in a quasi-monolithic Si environment

GaAs FET chips are planar embedded in a high resistivity silicon substrate and characterized up to 40 GHz in a coplanar environment. Hybrid interconnects (bonding wires) are replaced by thin film ones (air bridges). Small signal equivalent circuit extraction results confirm the expected low parasitic inductance values. These are reduced by more than 50% of the typical bonding wire interconnects

12 GHz coplanar quasi-monolithic oscillator

First results on coplanar quasi-monolithic (QM) circuits with GaAs FETs embedded in a silicon substrate are presented. Typical monolithic integration techniques are used for the fabrication of the passive circuitry and interconnects to the active devices. Measurements on a 12 GHz oscillator demonstrate the viability of the proposed technology

Minimum ion-beam exposure-dose determination for chemically amplified resist from printed dot matrices

Matrices of 90 nm dots have been printed into high-sensitivity positive resist (UVII HS, Shipley) with an ion projection system (IMS Vienna) to investigate the influence of shot noise on the printing probability of dots. Dot defect probability increases with diminishing ion dose following a Poisson distribution which demonstrates that shot noise is the dominating effect. The minimum ion numbers per dot to generate 50% defect probability are Ncrit=115 for standard resist treatment. This corresponds to N=165 for smaller defect probabilities of 10-4. Resist sensitivity was decreased with postexposure bake temperatures of 110 degrees C instead of 140 degrees C to improve the resolution capability of the resist. Under these conditions, and an additional resist top coat, Ncrit=130 ions per dot have been measured. The article demonstrates that ion projection lithography is not limited by shot noise at minimum resolution elements of 90 nm diam. The corresponding exposure doses are 0.3 mu C/cm2

Air bridge based planar hybrid technology for microwave and millimeterwave applications

A new silicon based, planar hybrid technology is being developed to address limitations associated with packaging and interconnections. The approach combines the advantages of both hybrid and monolithic technologies. Microwave transistor chips (GaAs FETs) are integrated in high resistivity silicon substrates with a vertical precision of better than 2 /spl mu/m and lateral tolerances less than 10 /spl mu/m. Air bridge technology and thin film techniques are then used to provide the necessary interconnections. The basic features of the proposed technology are presented here

Hierarchical interconnections in the nano-composite material bone: Fibrillar cross-links resist fracture on several length scales

Bone is a complex and very important multi-constituent bio-composite. In this work, we focus on the arrangement of bone constituents from the nanoscopic to the microscopic scale, and investigate the influence of their arrangements on the fracture mechanisms of the whole composite. We find that bone, on the nanoscopic scale, consists of mineralized collagen fibrils held together by a non-fibrillar organic matrix, which results in a primary failure mode of delamination between mineralized fibrils. In turn, these mineralized fibrils form one of three types of filaments that span microcracks in fractured bone samples, possibly resisting the propagation of these cracks. (c) 2005 Elsevier Ltd. All rights reserved