This paper analyzes the structures of organic layers that are obtained on metals or carbon by electrochemical reduction of diazonium salts or by simple dipping of the substrate in a diazonium solution.There is a general agreement in the literature on the polyphenylene structure of these layers. But, previous results based on XPS data have indicated the possible presence of azo groups in these layers. IR and TOF-SIMS experiments demonstrate the existence of these azo groups included in the polyphenylene chains. A mechanism is presented that accounts both for the growth of polyphenylene chains and the inclusion of azo bonds in these chains.

We report on a strain-induced phase transformation in Ge nanowires under external shear stresses. The resulted polytype heterostructure may have great potential for photonics and thermoelectric applications. ⟨111⟩-oriented Ge nanowires with standard diamond structure (3C) undergo a phase transformation toward the hexagonal diamond phase referred as the 2H-allotrope. The phase transformation occurs heterogeneously on shear bands along the length of the nanowire. The structure meets the common phenomenological criteria of a martensitic phase transformation. This point is discussed to initiate an on going debate on the transformation mechanisms. The process results in unprecedented quasiperiodic heterostructures 3C/2H along the Ge nanowire. The thermal stability of those 2H domains is also studied under annealing up to 650 °C by in situ TEM.