We established locally varying strain fields in unmodified MoS nanosheets. The approach relies on dry release in place of multilayer MoS on textured Si substrates. By this process we demonstrated intense photoluminescence, a ∼70 meV decrease of the transition energy, and exciton funneling in ∼4 nm-thick MoS films.

Graphene grown directly on Ge via chemical vapor deposition (CVD) can passivate the underlying Ge surface, preventing its oxidation in ambient air for at least months. However, the factors that govern oxidation of Ge coated with graphene have not been elucidated. We investigate the effect of graphene synthesis parameters and Ge surface orientation on passivation of Ge and correlate these data with the density and type of defects in graphene. Oxidation of Ge can be reduced by increasing the H2:CH4 flux ratio or decreasing the growth rate, which decrease the density of atomic-scale defects, such as point defects and grain boundaries, in graphene. Oxidation of graphene is concomitant with oxidation of Ge and occurs more readily when the density of atomic-scale defects is relatively high. Passivation of Ge, however, depends more strongly on Ge surface orientation, as Ge(110) oxidizes significantly less than Ge(001) or Ge(111), even at the same graphene defect density. These results provide a pathway for engineering high-quality graphene films on Ge, which may enable improved passivation of Ge and direct integration of graphene-based or hybrid graphene/Ge heterostructure devices on conventional semiconductor platforms.

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Antimonide compounds are fabricated in membrane form to enable materials combinations that cannot be obtained by direct growth and to support strain fields that are not possible in the bulk. InAs/(InAs,Ga)Sb type II superlattices (T2SLs) with different in-plane geometries are transferred from a GaSb substrate to a variety of hosts, including Si, polydimethylsiloxane, and metalcoated substrates. Electron microscopy shows structural integrity of transferred membranes with thickness of 100 nm to 2.5 µm and lateral sizes from 24 × 24 µm 2 to 1 × 1 cm 2 . Electron microscopy reveals the excellent quality of the membrane interface with the new host. The crystalline structure of the T2SL is not altered by the fabrication process, and a minimal elastic relaxation occurs during the release step, as demonstrated by X-ray diffraction and mechanical modeling. A method to locally strain-engineer antimonide-based membranes is theoretically illustrated. Continuum elasticity theory shows that up to ∼3.5% compressive strain can be induced in an InSb quantum well through external bending. Photoluminescence spectroscopy and characterization of an IR photodetector based on InAs/GaSb bonded to Si demonstrate the functionality of transferred membranes in the IR range.antimonide | membranes | transfer | infrared | integration E pitaxially grown Sb compounds have recently received increasing attention as functional layers in IR detectors (1-4) and sources (5-9), high-mobility transistors (10-12), resonant tunneling diodes (13-15), and low-power analog and digital electronics (10,16). In this scenario we establish a versatile process to release and transfer Sb-based heterostructures from their epitaxial growth substrate to any host, resulting in fabrication of freestanding membranes (17,18). Despite the numerous demonstrations of membrane technology applied to III-V semiconductors (18-26), fabrication and detailed characterization of Sb compounds in membrane form has not been reported. For the purpose of this work we investigate InAs/(Ga,InAs)Sb type II superlattices (T2SLs) and AlInSb/InSb quantum wells (QWs), but our approach is readily applicable to any Sb-containing heterostructure. We demonstrate that wet and dry techniques (17, 18) (i.e., transfer in liquid or mediated by a stamp, respectively) yield successful transfer of T2SL membranes with thickness ranging from 100 nm to 2.5 µm, and lateral sizes going from 24 × 24 µm 2 to 1 × 1 cm 2 . We bond InAs/(InAs,Ga)Sb T2SLs to a large variety of hosts, including elastomers and rigid substrates, and both insulating and semiconducting substrates. Electron microscopy and X-ray diffraction (XRD) show that the crystal structure and the strain state of the materials are minimally altered during the release and transfer process. Mechanical modeling establishes that elastic strain up to ∼3.5% can be imparted in nanoscale-thickness AlInSb/InSb/AlInSb membranes by external bending. Finally, we demonstrate the functionality of Sbbased superlattices bonded to Si via photoluminescence (PL) and cha...

Charge carrier transport in thin hydrogen (H)-terminated Si(001) sheets is explored via a fourprobe device fabricated on silicon-on-insulator (SOI) using the bulk host Si as a back-gate. The method enables electrical measurements without a need to contact the sample surface proper. Sheet conductance measurements as a function of back-gate voltage demonstrate the presence of acceptor and donor-like surface states. These states are distributed throughout the gap and can be