STM/STS Observation on Layered Nitride Superconductor [alpha]-(DDA) sub(x)TiNCl

Scanning tunneling microscopy/spectroscopy (STM/STS) measurements on [alpha]-(DDA) sub(x)TiNCl (DDA=H sub(2)N-(CH sub(2)) sub(10)-NH sub(2), T sub(c)=16 K) have been carried out. The STM topography exhibits simple rectangular shaped atomic lattice with the periods of |a|=0.38 nm and |b|=0.33 nm. The averaged dI/dV spectrum shows the gap value of [Delta] ~ 9 meV, giving an unusual large gap ratio 2[Delta]=k sub(B)T sub(c) [Asymptotically = to] 13. The STS results show the bar-shaped domain structures along the b-axis direction in the bias range of V = +5 ~ +15 mV, demonstrating the possible existence of intercalated molecules.