We demonstrate the feasibility of fabricating heterojunctions of semiconductors with high mismatches in lattice constant and coefficient of thermal expansion by employing nanomembrane bonding. We investigate the structure of and electrical transport across the interface of a Si/Ge bilayer formed by direct, low-temperature hydrophobic bonding of a 200 nm thick monocrystalline Si(001) membrane to a bulk Ge(001) wafer. The membrane bond has an extremely high quality, with an interfacial region of ∼1 nm. No fracture or delamination is observed for temperature changes greater than 350 °C, despite the approximately 2:1 ratio of thermal-expansion coefficients. Both the Si and the Ge maintain a high degree of crystallinity. The junction is highly conductive. The nonlinear transport behavior is fit with a tunneling model, and the bonding behavior is explained with nanomembrane mechanics.

We used reverse Monte Carlo (RMC) modeling to simulate the atomic structure of a Zr-based bulk metallic glass (BMG), incorporating short-range structural data from the electron diffraction total reduced density functionG(r) and medium-range structural data from fluctuation electron microscopy (FEM). Including the FEM data created within the model loosely ordered planar atomic arrangements covering regions ∼1 nm in diameter without degrading the agreement withG(r). RMC refinement against onlyG(r) produced no agreement with FEM. Improved simulations are needed to create fully realistic BMG structures, but these results show that including FEM in RMC further constrains the structure compared withG(r) data alone and that the FEM signal in real materials is likely to arise from pseudo-planar arrangements of atoms.

Thin-film deposition on ultra-thin substrates poses unique challenges because of the potential for a dynamic response to the film stress during deposition. While theoretical studies have investigated film stress related changes in the substrate, little has been done to learn how stress might evolve in a film growing on a compliant substrate. We use silicon nanomembranes (SiNMs), extremely thin sheets of single-crystalline Si, as a substrate for the growth of amorphous SiN x to begin to address this question. Nanomembranes are released from a silicon-oninsulator wafer with selective etching, transferred over a hole etched into a Si wafer, and bonded to the edges of the hole. The nanomembrane window provides the substrate for SiN x deposition and a platform, using Raman spectroscopy, for measurements of the evolving strain in the nanomembrane. From the strain in the nanomembrane, the film stress can be inferred from the required balance of forces in the film/substrate system. We observe that the strain in the tethered 2 NM increases as the NM is made thinner while the intrinsic steady-state stress in the deposited film is reduced.

An approach has been developed to produce silver nanoparticles (AgNPs) rapidly on semiconductor wafers using electrochemical deposition. The closely packed AgNPs have a density of up to 1.4 × 1011 cm-2 with good size uniformity. AgNPs retain their shape and position on the substrate when used as nanomasks for producing ultrahigh-density vertical nanowire arrays with controllable size, making it a one-step nanolithography technique. We demonstrate this method on Si/SiGe multilayer superlattices using electrochemical nanopatterning and plasma etching to obtain high-density Si/SiGe multilayer superlattice nanowires.