The use of information retrieval systems in networked environments raises a new set of issues that have received little attention.

The controlled synthesis of high-quality multilayer (ML) MoS flakes with gradually shrinking basal planes by chemical vapor deposition (CVD) is demonstrated. These CVD-grown ML MoS flakes exhibit much higher mobility and current density than mechanically exfoliated ML flakes due to the reduced contact resistance which mainly resulted from direct contact between the lower MoS layers and electrodes.

Developing controlled approaches for synthesizing high-quality two-dimensional (2D) semiconductors is essential for their practical applications in novel electronics. The application of chemical vapor transport (CVT), an old single-crystal growth technique, has been extended from growing 3D crystals to synthesizing 2D atomic layers by tuning the growth kinetics. Both single crystalline individual flakes and continuous films of 1 L MoS were successfully obtained with CVT approach at low growth temperatures of 300-600 °C. The obtained 1 L MoS exhibits high crystallinity and comparable mobility to mechanically exfoliated samples, as confirmed by both atomic resolution microscopic imaging and electrical transport measurements. Besides MoS , this method was also used in the growth of 2D WS , MoSe , Mo W S alloys, and ReS , thus opening up a new way for the controlled synthesis of various 2D semiconductors.

Two-dimensional (2D) metallic transition metal dichalcogenides (TMDCs), such as 1T-TiSe, are ideal systems for exploring the fundamentals in condensed matter physics. However, controlled synthesis of these ultrathin materials has not been achieved. Here, we explored the synthesis of charge density wave (CDW)-bearing 2D TiSe with chemical vapor transport (CVT) by extending this bulk crystal growth approach to the surface growth of TiSe by introducing suitable growth substrates and dramatically slowing down the growth rate. Sub-10 nm TiSe flakes were successfully obtained, showing comparable quality to the mechanically exfoliated thin flakes. A CDW state with 2 × 2 superstructure was clearly observed on these ultrathin flakes by scanning tunneling microscopy (STM), and the phase transition temperature of these flakes was investigated by transport measurements, confirming the existence of CDW states. Our work opens up a new approach to synthesizing 2D CDW and superconductive TMDCs for exploring new fundamentals and applications in novel electronics.

The mechanical robustness of atomic layer deposited alumina and recently developed molecular layer deposited aluminum alkoxide ͑"alucone"͒ films, as well as laminated composite films composed of both materials, was characterized using mechanical tensile tests along with a recently developed fluorescent tag to visualize channel cracks in the transparent films. All coatings were deposited on polyethylene naphthalate substrates and demonstrated a similar evolution of damage morphology according to applied strain, including channel crack initiation, crack propagation at the critical strain, crack densification up to saturation, and transverse crack formation associated with buckling and delamination. From measurements of crack density versus applied tensile strain coupled with a fracture mechanics model, the mode I fracture toughness of alumina and alucone films was determined to be K IC = 1.89Ϯ 0.10 and 0.17Ϯ 0.02 MPa m 0.5 , respectively. From measurements of the saturated crack density, the critical interfacial shear stress was estimated to be c = 39.5Ϯ 8.3 and 66.6Ϯ 6.1 MPa, respectively. The toughness of nanometer-scale alumina was comparable to that of alumina thin films grown using other techniques, whereas alucone was quite brittle. The use of alucone as a spacer layer between alumina films was not found to increase the critical strain at fracture for the composite films. This performance is attributed to the low toughness of alucone. The experimental results were supported by companion simulations using fracture mechanics formalism for multilayer films. To aid future development, the modeling method was used to study the increase in the toughness and elastic modulus of the spacer layer required to render improved critical strain at fracture. These results may be applied to a broad variety of multilayer material systems composed of ceramic and spacer layers to yield robust coatings for use in chemical barrier and other applications.Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.