We explored a noninvasive optical method to determine the Joule heating of individual germanium nanowires. Using confocal μ-Raman spectroscopy, variations in the optical phonon frequency, in detail the downshifting of the first-order Stokes Raman band, are correlated to the temperature increase of vapor-liquid-solid grown germanium nanowires under an applied electrical bias. The germanium nanowires were found to handle high threshold current densities of more than 10~6 A cm~(-2) before sustaining immediate deterioration. Failure of single crystalline germanium nanowires was directly observed when the applied electric field reached the breakdown point of 1.25 × 10~5 V cm~(-1).
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机译：我们探索了一种非侵入式光学方法来确定单个锗纳米线的焦耳热。使用共焦μ-拉曼光谱，光子声子频率的变化，尤其是一阶斯托克斯拉曼能谱的下移，与在施加电偏压下汽-液-固生长的锗纳米线的温度升高相关。发现锗纳米线在承受立即恶化之前，可以处理超过10〜6 A cm〜（-2）的高阈值电流密度。当施加的电场达到击穿点1.25×10〜5 V cm〜（-1）时，直接观察到单晶锗纳米线的失效。
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