  Plasma enhanced chemical vapor deposition (PECVD) techniques have been shown
to be an efficient method to achieve single-step synthesis of high-quality
monolayer graphene (MLG) without the need of active heating. Here we report
PECVD-growth of single-crystalline hexagonal bilayer graphene (BLG) flakes and
mm-size BLG films with the interlayer twist angle controlled by the growth
parameters. The twist angle has been determined by three experimental
approaches, including direct measurement of the relative orientation of
crystalline edges between two stacked monolayers by scanning electron
microscopy, analysis of the twist angle-dependent Raman spectral
characteristics, and measurement of the Moir\'e period with scanning tunneling
microscopy. In mm-sized twisted BLG (tBLG) films, the average twist angle can
be controlled from 0 to approximately 20 \degree, and the angular spread for a
given growth condition can be limited to < 7 \degree. Different work functions
between MLG and BLG have been verified by the Kelvin probe force microscopy and
ultraviolet photoelectron spectroscopy. Electrical measurements of back-gated
field-effect-transistor devices based on small-angle tBLG samples revealed
high-quality electric characteristics at 300 K and insulating temperature
dependence down to 100 K. This controlled PECVD-growth of tBLG thus provides an
efficient approach to investigate the effect of varying Moir\'e potentials on
tBLG.
