Fig. 4. TEM images of Cu/BN with varied Cu contents (a–d); zoom-in HRTEM images with FFT patterns on corresponding BN of Cu/BN samples (a′–d′). (a) and (a′) BN; (b) and (b′) 1% Cu/BN; (c) and (c′) 5% Cu/BN; (d) and (d′)10% Cu/BN.