  Molybdenum ditelluride (MoTe$_2$) has attracted considerable interest for
nanoelectronic, optoelectronic, spintronic, and valleytronic applications
because of its modest band gap, high field-effect mobility, large
spin-orbit-coupling splitting, and tunable 1T'/2H phases. However, synthesizing
large-area, high-quality MoTe$_2$ remains challenging. The complicated design
of gas-phase reactant transport and reaction for chemical vapor deposition or
tellurization is nontrivial because of the weak bonding energy between Mo and
Te. Here, we report a new method for depositing MoTe$_2$ that entails using
physical vapor deposition followed by a post-annealing process in a Te-free
atmosphere. Both Mo and Te were physically deposited onto the substrate by
sputtering a MoTe$_2$ target. A composite SiO$_2$ capping layer was designed to
prevent Te sublimation during the post-annealing process. The post-annealing
process facilitated 1T'-to-2H phase transition and solid-phase crystallization,
leading to the formation of high-crystallinity few-layer 2H-MoTe$_2$ with a
field-effect mobility of ~10 cm$^2$/(V-s), the highest among all nonexfoliated
2H-MoTe$_2$ currently reported. Furthermore, 2H-MoS$_2$ and Td-WTe$_2$ can be
deposited using similar methods. Requiring no transfer or chemical reaction of
metal and chalcogen reactants in the gas phase, the proposed method is
potentially a general yet simple approach for depositing a wide variety of
large-area, high-quality, two-dimensional layered structures.
