  In view of their immensely intriguing properties, two dimensional materials
are being intensely researched in search of novel phenomena and diverse
application interests, however, studies on the realization of nanocomposites in
the application-worthy thin-film platform are rare. Here we have grown MoS2-hBN
composite thin films on different substrates by the pulsed laser deposition
technique and made comparative studies with the pristine MoS2 and hBN films.
The Raman, XPS and HRTEM confirm the concomitant presence of both the 1T
(conducting) and 2H (semiconducting) polymorphs of MoS2 in the composite film.
Interestingly, a peculiar reentrant semiconductor-metal-insulator transition is
seen in the composite film which is absent in the MoS2 film, and it correlates
well with the signatures of phonon softening seen in temperature-dependent
Raman spectroscopy. Furthermore, electrostatic force microscopy reveals the
presence of three distinct regions (metallic, semiconducting, and insulating)
in the composite film with differing contact potentials and enhanced propensity
for charge transfer with respect to pristine MoS2. A triboelectric
nanogenerator device containing biphasic composite film as an electron acceptor
exhibits more than twofold (sixfold) enhancement in peak-to-peak output voltage
as compared to the pristine MoS2 (hBN) film. These observations bring out the
potential of nanocomposite thin films for unfolding emergent phenomena and
technological applications.
