Form of Scaling Function in Quantum Hall Plateau Transitions

We have measured the temperature dependence of the resistance Rxx and Rxy of a two-dimensional electron system in the regime of the quantum Hall plateau transition. We observe for our sample a considerable large critical exponent κ～ 0.66 - 0.77, which may be due to the dominant electron-phonon scattering. Further we find a simple exponential form of Rxx = Rc exp（-s） in agreement with the theoretically proposed universal scaling function.