  In this letter, we propose that the narrowband photodetection can be realized
in the skin layer of semiconductors with the spatially separated photo-excited
carriers from the nanoscale heterolattice electronic transitions (NanoHLETs).
The NanoHLET photodetection is demonstrated by measuring the photoconductive
responses of the $\sim$ 1 $\mu$m thick films of TiO$_{2}$ glass embedded with
rutile and anatase TiO$_{2}$ nanocrystals. As containing only rutile
nanocrystals, the TiO$_{2}$ glass film presents the responsivity curve with
only one sharp peak centered at 423.0 nm with a full-width-at-half-maximum
(FWHM) of 13.7 nm. This NanoHLET mechanism may open a new way in making
ultra-small narrow-band photodetectors matching the current nanoscale
electronic technology.
