  We present the results of a deep (J ~ 21 mag at 5 sigma) infrared photometric
survey of a 0.95 square degree area in the central region of the Upper Sco
association. The photometric observations consist of a deep (Y+J)-band images
obtained with the WFCAM camera on the UKIRT InfraRed Telescope (UKIRT) with
partly coverage in Z complemented by methane ON and OFF conducted with WIRCam
on the Canada France Hawaii Telescope. We have selected five potential T-type
objects belonging to the Upper Sco association on the basis of their blue
methane colours and their J-CH4off colours. We have also identified a sample of
7-8 Upper Sco member candidates bridging the gap between known cluster M-types
and our new T-type candidates. These candidates were selected based on their
positions in various colour-magnitude diagrams and they follow the sequence of
known Upper Sco members identified in the UKIRT Infrared Deep Sky Survey
(UKIDSS) Galactic Clusters Survey (GCS). We present additional membership
constraints using proper motion estimates from the multiple epochs available to
us. We also present optical and near-infrared spectra obtained with the
X--Shooter spectrograph on the Very Large Telescope for five L-type candidates
covering the 0.6 to 2.5 micron wavelength range, none of them being confirmed
as a young brown dwarf. We discuss the lack of detection of new candidate
members as well as the possible turn down in the USco mass function as we are
approaching the fragmentation limit.
