Miao and Zhang Nanoscale Research Letters 2012, 7:321 http://www.nanoscalereslett.com/content/7/1/321 Page 5 of 6 Figure 5 Room-temperature Raman spectra of InP nanowires at different growing stages. Nanowires grown for (a) 2, (b) 5, (c) 7, and (d) 15 min. is the existence of the space for accumulating TMIn and decomposed on the surface. The new nanowires fabri- cated in the nanowire growing process have the same crystal structure with the nanowires grown on the in- dium droplets. The nanowires exhibited that room- temperature photoluminescence blueshifted from the bulk zinc blende InP bandgap energy. The bandgap of the nanowires has direct relations with the diameter. In the nanowire growth, the bandgap of the nanowires can be modulated by adjusting the diameter of the nano- wires. Controlling the nanowire growing time or the size of the catalyst will be possible. The crystal quality of the InP nanowires at different growing stages is a dynamic process. These results verify and supplement the re- search on catalyst-free InP nanowire growth. Abbreviations LO: longitudinal optical phonon; MOCVD: metal organic chemical vapor deposition; PH3: phosphine; PL: photoluminescence; SEM: scanning electron microscopy; TMIn: trimethylindium; TO: transverse optical phonon. Competing interests The authors declare that they have no competing interests. Acknowledgments This work was partly supported by the National Key Basic Research Program of China (Grant No. 2012CB619200) and the National Natural Science Foundation of China (Grant No. 50972141). Authors’ contributions GQM and DWZ conceived the study, participated in its design, and drafted the manuscript. Both authors carried out the experiments. GQM revised the manuscript. Both authors read and approved the final manuscript. Authors’ information GQM is a professor and DWZ is an assistant professor in the State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dongnanhu Road, Changchun 130033, People’s Republic of China. Received: 27 April 2012 Accepted: 20 June 2012 Published: 20 June 2012 References 1. Keiichi H, Toshio K, Kenji H, Kensuke O: GaAs p-n junction formed in quantum wire crystals. Appl Phys Lett 1992, 60:745–747. 2. Duan XF, Huang Y, Cui Y, Wang JF, Lieber CM: Indium phosphide nanowires as building blocks for nanoscale electronic and optoelectronic devices. Nature 2001, 409:66–69. 3. Duan XF, Huang Y, Agarwal R, Lieber CM: Single-nanowire electrically driven lasers. Nature 2003, 421:241–245. 4. Björk MT, Ohlsson BJ, Thelander C, Persson AI, Deppert K, Wallenberg LR, Samuelson L: Nanowire resonant tunneling diodes. Appl Phys Lett 2002, 81:4458–4460. 5. Thelander C, Mårtensson T, Björk MT, Ohlsson BJ, Larsson MW, Wallenberg LR, Samuelson L: Single-electron transistors in heterostructure nanowires. Appl Phys Lett 2003, 83:2052–2054. 6. Oliver H, Ritesh A, Wei L: Semiconductor nanowire devices. Nanotoday 2008, 3:12–22. 7. Wagner RS, Ellis WC: Vapor–liquid-solid mechanism of single crystal growth. Appl Phys Lett 1964, 4:89–90. 8. Werner S, Magnus B, Knut D, Kimberly AD, Jonas J, Magnus WL, Thomas M, Niklas S, Svenssona CPT, Wacasera BA, Wallenbergb LR, Lars S: Growth of one-dimensional nanostructures in MOVPE. J Cryst Growth 2004, 272:211–220. 9. Thomas M, Svensson CPT, Wacaser B, Magnus WL, Werner S, Knut D, Anders G, Wallenberg LR, Lars S: Epitaxial III − V nanowires on silicon. Nano Lett 2004, 4:1987–1990. 10. Collins CB, Carlson RO, Gallagher CJ: Properties of gold-doped silicon. Phys Rev 1957, 105:1168–1173. 11. Hannon JB, Kodambaka S, Ross FM, Tromp RM: The influence of the surface migration of gold on the growth of silicon nanowires. Nature (London) 2006, 440:69–71.