Scanning Electron Microscopy


In semiconducting materials with current controlled negative differential conductivity an inhomogeneous current density distribution can arise leading to a well-defined spatial pattern in the form of current filaments. Detailed experiments are performed on silicon pin diodes showing a pronounced multistability in the current voltage characteristics. By using the voltage contrast and the electron beam induced voltage (EBIV) methods in a SEM, it is confirmed that each jump in the current is accompanied with the formation or disappearance of a well defined transverse electrical structure between the two contacts as a result of a current filament. This non-uniform state of the material is found to exhibit a clear solitary structure. The observed voltage oscillations are traced back to instabilities of this spatial structure.

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