  The charge-density-wave (CDW) phase is a macroscopic quantum state consisting
of a periodic modulation of the electronic charge density accompanied by a
periodic distortion of the atomic lattice in quasi-1D or layered 2D metallic
crystals. Several layered transition metal dichalcogenides, such as 1T-TaSe2,
1T-TaS2 and 1T-TiSe2, exhibit unusually high transition temperatures to
different CDW symmetry-reducing phases. These transitions can be affected by
environmental conditions, film thickness and applied electric bias. However,
device applications of these intriguing systems at room temperature or their
integration with other 2D materials have not been explored. Here we show that
in 2D CDW 1T-TaS2, the abrupt change in the electrical conductivity and
hysteresis at the transition point between nearly-commensurate and
incommensurate charge-density-wave phases can be used for constructing an
oscillator that operates at room temperature. The hexagonal boron nitride was
capped on 1T-TaS2 thin film to provide protection from oxidation, and an
integrated graphene transistor provides a voltage tunable, matched,
low-resistance load enabling precise voltage control of the oscillator
frequency. The integration of these three disparate two-dimensional materials,
in a way that exploits the unique properties of each, yields a simple,
miniaturized, voltage-controlled oscillator device. Theoretical considerations
suggest that the upper limit of oscillation frequency to be in the THz regime.
