Schottky barrier modulation of bottom contact SnO_(2) thin-film transistors via chloride-based combustion synthesis

The enhanced carrier flow at the interface between Au and SnO_(2)semiconductors,which initially form Schottky contacts,is realized using chloride-based combustion synthesis.Chloride-based combustion sys-tems can achieve chlorine(Cl)doping effects as well as conversion to crystalline SnO_(2)films at clearly lower temperatures(∼250℃)than conventional precursors.Due to the Cl doping effect,the high carrier concentration can induce thin potential barriers at the metal/semiconductor(MS)junctions,resulting in carrier injection by tunneling.As a result,compared to conventional SnO_(2)thin-film transistors,the de-vices fabricated by combustion synthesis exhibit significantly improved electrical performance with field-effect mobility of 6.52 cm 2/Vs(∼13 times),subthreshold swing of 0.74 V/dec,and on/offratio of∼10^(7)below 300℃.Furthermore,because of the enhanced tunneling carriers induced by the narrowed barrier width,the Schottky barriers are significantly reduced from 0.83 to 0.29 eV(65%decrease)at 250℃and from 0.42 to 0.17 eV(60%decrease)at 400℃.Therefore,chloride-based combustion synthesis can con-tribute to developing SnO_(2)-based electronics and flexible devices by achieving both high-quality oxide films and improved current flow at the MS interface with low-temperature annealing.

Releasing the hidden shift current in the TTF-CA organic molecular solid via symmetry lowering

Bulk photovoltaic effect,characterized by an excitation-driven unbiased spontaneous photocurrent,has attracted substantial attention mainly due to its potential for harvesting solar energy.Here,we investigate the photovoltaic characteristics of organic molecular solids and focus on the association between the photocurrent and the crystal symmetry in the exemplary case of tetrathiafulvalene-p-chloranil.We perform comprehensive first-principles calculations,including direct evaluations of the excitedstate current via real-time propagations of the time-dependent density functional theory.We find that the charge shifting in the low-temperature phase is mainly driven by the intrachain ferroelectricity,which gives rise to a photocurrent not only in the visiblelight range but also near the band-edge infrared region.The shift current that is locked in the symmetry of the high-temperature phase can be released by introducing a potential asymmetry.We suggest that organic molecular solids can be exploited via appropriate engineering to lower the symmetry,aiming at room-temperature photovoltaics.