Study of interfacial random strain fields in core-shell ZnO nanowires by scanning transmission electron microscopy.

•Random strain fields in core-shell ZnO nanowires are directly imaged by the STEM techniques.•Origin of the strain contrast is discussed based on measured and simulated STEM images.•Strain contrast strongly depends on sample thickness and collection angles of the ADF detector.•Optimum experimental parameters for imaging random strain fields is proposed for different samples.