A theoretical study of blue phosphorene nanoribbons based on   first-principles calculations
  Based on first-principles calculations, we present a quantum confinement mechanism for the band gaps of blue phosphorene nanoribbons (BPNRs) as a function of their widths. The BPNRs considered have either armchair or zigzag shaped edges on both sides with hydrogen saturation. Both the two types of nanoribbons are shown to be indirect semiconductors. An enhanced energy gap of around 1 eV can be realized when the width decreases to about 10 ang. The underlying physics is ascribed to the quantum confinement. More importantly, the quantum confinement parameters are obtained by fitting the calculated gaps with respect to their widths. The results show that the quantum confinement in armchair nanoribbons is stronger than that in zigzag ones. This study provides an efficient approach to tune the energy gap in BPNRs. 
Jiefeng Xie, M. S. Si, D. Z. Yang, Z. Y. Zhang, and D. S. Xue
cond-mat.mtrl-sci