Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, Texas 77005, USA.
Nat Nanotechnol. 2011 Jan;6(1):33-8. doi: 10.1038/nnano.2010.240. Epub 2010 Dec 12.
Understanding and controlling the flow of heat is a major challenge in nanoelectronics. When a junction is driven out of equilibrium by light or the flow of electric charge, the vibrational and electronic degrees of freedom are, in general, no longer described by a single temperature. Moreover, characterizing the steady-state vibrational and electronic distributions in situ is extremely challenging. Here, we show that surface-enhanced Raman emission may be used to determine the effective temperatures for both the vibrational modes and the electrons in the current in a biased metallic nanoscale junction decorated with molecules. Molecular vibrations show mode-specific pumping by both optical excitation and d.c. current, with effective temperatures exceeding several hundred kelvin. Anti-Stokes electronic Raman emission indicates that the effective electronic temperature at bias voltages of a few hundred millivolts can reach values up to three times the values measured when there is no current. The precise effective temperatures are model-dependent, but the trends as a function of bias conditions are robust, and allow direct comparisons with theories of nanoscale heating.
理解和控制热量的流动是纳米电子学的主要挑战。当结因光或电荷的流动而偏离平衡时，振动和电子自由度通常不再由单个温度来描述。此外，原位表征稳态振动和电子分布极具挑战性。在这里，我们表明，表面增强拉曼发射可用于确定带有分子的偏置金属纳米尺度结中电流的振动模式和电子的有效温度。分子振动通过光学激发和直流电流以模式特异性的方式进行泵浦，有效温度超过几百开尔文。反斯托克斯电子拉曼发射表明，在几百毫伏的偏置电压下，有效电子温度可达无电流时测量值的三倍。精确的有效温度取决于模型，但随着偏置条件的变化趋势是稳健的，并且允许与纳米尺度加热的理论进行直接比较。
