As an attractive dielectric material, polyimide has been widely used in the field of electronics, aerospace, and automobiles due to its useful mechanical properties and good chemical resistance. UV irradiation was considered to be the main factor related to the damage and failure of polyimide. Here the effects of UV irradiation on the surface morphology and microscale mechanical properties of polyimide films are characterized by atomic force microscopy (AFM). The surface roughness of the UV-irradiated samples developed and the mechanical properties degraded with the radiation dose increased. For comparison, uniaxial tensile test was performed to obtain the macroscale Young’s modulus of polyimide film. The UV-irradiated damaging depth was simulated with finite element method (FEM).

The effects of uniaxial strain on the structure, band gap and transmission carriers of monolayer phosphorene were investigated by first-principles calculations. The strain induced semiconductor-metal as well as direct-indirect transitions were studied in monolayer phosphorene. The position of CBM which belonged to indirect gap shifts along the direction of the applied strain. We have concluded the change rules of the carrier effective mass when plane strains are applied. In band structure, the sudden decrease of band gap or the new formation of CBM (VBM) causes the unexpected change in carrier effective mass. The effects of zigzag and armchair strain on the effective electron mass in phosphorene are different. The strain along zigzag direction has effects on the electrons effective mass along both zigzag and armchair direction. By contrast, armchair-direction strain seems to affect only on the free electron mass along zigzag direction. For the holes, the effective masses along zigzag direction are largely affected by plane strains while the effective mass along armchair direction exhibits independence in strain processing. The carrier density of monolayer phosphorene at 300 K is calculated about [Formula: see text] cm, which is greatly influenced by the temperature and strain. Strain engineering is an efficient method to improve the carrier density in phosphorene.