Charge TransferTransition metal dichalcogenides (TMDCs) belong to the class of various 2D materials which in bulk form are composed of strongly bonded layers with week van der Waals force among them, [1][2][3] allowing exfoliation into atomically thin layers whose properties can be distinct from their bulk counterparts. [1,4,5] TMDCs show a wide range of electronic, optical, mechanical, chemical, and thermal properties which have been studied for decades. [4] Intercalation of TMDCs is one important field in the chemistry of inclusion compounds. With guest materials such as alkali metals intercalated in the host ones, the structure Figure 4. Schematic illustration of the phase transition. a) structure of 2H-Na 0.5 MoS 2 and valence state of Mo. b) Schematic showing charge transfer between Mo 3+ and Mo 4+ and the charge transfer induced phase transition from 2H to 1T. www.advancedsciencenews.com

Platinum (Pt) composite nanowires were grown on the tip of tungsten (W) microprobes by focused-electron-beam induced chemical vapor deposition (FEB-CVD). An electrical field was used to drive a transversal mechanical vibration of the nanowires. Such nanowire vibrations were found to display the first and second harmonic resonances with frequencies in the range of tens of MHz. The Young's modulus of the nanowires was estimated to be in the range of (1.4 ± 0.1) × 102 GPa to (4.7 ± 0.2) × 102 GPa, dependent on the wire size. A mass responsivity of 2.1 × 1021 Hz/kg was demonstrated with the minimum detectable mass of about 0.4 attogram. Our results indicated the potentials of FEB-CVD for the fabrication of nano-balances on any surface for ultra-sensitive mechanical applications.

Understanding the evolution mechanisms of interlayer stacking structures, particularly at the atomic scale, is of great significance for modulating the physical properties and realizing the full potential of 2D materials in electronics and quantum information applications. Herein, by performing in situ experiments using aberration corrected scanning transmission electron microscopy, the evolution of diverse interlayer stacking sequences (from 3R to N, N to 3R and N(3R) to AB′-stacked) in bilayer PtSe2 are directly observed. Furthermore, the interlayer rotational angles are tuned (e.g. 13.3° to 9.4°, 16.8° to 11° and 16.1° to 6°) in situ at real time in bilayer PtSe2. Density functional theory calculations reveal a small energy barrier (<0.2 eV per formula unit) for the kinetic evolution of interlayer structures. The illumination electron beam, while being as an atomic-scale probe for imaging, transfers enough energy initiating the transition. The bilayer PtSe2 has show the rich stacking and twisted structures which may create novel physical phenomena. These findings shed new light on the diversity of structural properties of bilayer PtSe2, which may be valuable for constituting a step further toward their potential uses for next generation of 2D transition metal dichalcogenides-based device applications.