Fracture experiments to evaluate the cleavage energy of the (110) [110] and (111) [112] cleavage systems in silicon at room temperature and humidity give 2.7 +/- 0.3 and 2.2 +/- 0.2 J/m(2), respectively, lower than any previous measurement and inconsistent with density functional theory ( DFT) surface energy calculations of 3.46 and 2.88 J=m(2). However, in an inert gas environment, we measure values of 3.5 +/- 0.2 and 2.9 +/- 0.2 J=m(2), consistent with DFT, that suggest a previously undetected stress corrosion cracking scenario for Si crack initiation in room conditions. This is fully confirmed by hybrid quantum-mechanics molecular-mechanics calculations.
