Browsing by Author "Lan, ZH"

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Growth of single-crystalline wurtzite aluminum nitride nanotips with a self-selective apex angle
(2005-05-01)
Shi, SC
;
Chen, CF
;
Chattopadhyay, S
;
Lan, ZH
;
Chen, KH
Single-crystal line, hexagonal aluminum nitride nanotips are fabricated using a vapor-transport and condensation process (VTCP) on silicon substrates with or without a catalyst layer. The resultant tips have very sharp nanoscale apexes (&SIM; 1 nm), while their bases and lengths are up to hundreds of nanometers wide and several micrometers long, respectively. It has been demonstrated that the thickness of the gold-catalyst layer plays a critical role in controlling the size of the tip; in addition, a catalyst-free growth mode has been observed, which results in lesser control over the nanotip morphology. Nevertheless, a remarkably narrow distribution of the apex angle of the nanotips, regardless of whether or not a catalyst was used in the VTCP, has been obtained. Compared with the commonly observed ridge and pyramid structures, the nanotips produced by VTCP have higher angles (&SIM; 81&DEG;) between the tilted (221) and the basal (001) planes that encase it. A mechanism for this self-selective apex angle in aluminum nitride nanotip growth is proposed.
Molecular sensing with ultrafine silver crystals on hexagonal aluminum nitride nanorod templates
(2005-03-09)
Chattopadhyay, S
;
Shi, SC
;
Lan, ZH
;
Chen, CF
;
Chen, KH
Reduced temperature-quenching of photoluminescence from indium nitride nanotips grown by metalorganic chemical vapor deposition
(2005-11-14)
Shi, SC
;
Chen, CF
;
Hsu, GM
;
Hwang, JS
;
Chattopadhyay, S
We report metalorganic chemical vapor deposition of indium nitride (InN) nanotips with apex angles of 10 degrees and length and base diameter of around 1 mu m and 200 nm, respectively. The structure of the hexagonal InN nanotips growing along [002] was studied by electron microscopy and x-ray diffraction, and the optical properties were studied using temperature-dependent photoluminescence (PL) measurements. A narrow emission peak with a 18 meV full width at half maximum positioned at 0.77 eV was obtained with no visible emission. A PL quenching of only 14% was observed with a temperature scan of 15-320 K. (C) 2005 American Institute of Physics.