MODULATION OF THE CRYSTAL-STRUCTURE IN QUASI-ONE-DIMENSIONAL SOLIDS INDUCED BY IMPURITIES - AN ATOMIC-FORCE MICROSCOPE STUDY

An atomic-force microscope study of interstitial impurities in the qua si-one-dimensional charge-density-wave system NbSe3 at room temperatur e (in the normal phase) exhibits long-range periodic lattice modulatio ns. The amplitudes and wavelengths are strong functions of the impurit y concentration, and in the case-of vanadium successive wavelengths of 6b0, 4b0, and 3b0 are observed. The drastic changes in the long-range structure of the system caused by small changes in the impurity conce ntration are an indication of the complex electric susceptibility of a system on the verge of becoming unstable against charge-density-wave formation.