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A Novel Way for Synthesizing Phosphorus-Doped Zno Nanowires

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ABSTRACT

We developed a novel approach to synthesize phosphorus (P)-doped ZnO nanowires by directly decomposing zinc phosphate powder. The samples were demonstrated to be P-doped ZnO nanowires by using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectra, X-ray photoelectron spectroscopy, energy dispersive spectrum, Raman spectra and photoluminescence measurements. The chemical state of P was investigated by electron energy loss spectroscopy (EELS) analyses in individual ZnO nanowires. P was found to substitute at oxygen sites (PO), with the presence of anti-site P on Zn sites (PZn). P-doped ZnO nanowires were high resistance and the related P-doping mechanism was discussed by combining EELS results with electrical measurements, structure characterization and photoluminescence measurements. Our method provides an efficient way of synthesizing P-doped ZnO nanowires and the results help to understand the P-doping mechanism.

No MeSH data available.


a IDS–VDS plots of P-doped ZnO nanowire FETs measured under UV illumination. Inset: The schematic illustration of the measured device b IDS–VDS plot of the P-doped ZnO nanowire FETs transistor with platinum electrodes. Lower right inset: Enlarged IDS–VDScurve in dark. Upper left inset: SEM image of a typical device c NBE of pure and P-doped ZnO nanowires at 10 K. Inset: enlarged part of the peaks around 3.31 eV for P-doped ZnO nanowires d Temperature-dependent PL spectra of P-doped ZnO nanowires with the evolution of two separate peaks around 3.31 eV.
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Figure 3: a IDS–VDS plots of P-doped ZnO nanowire FETs measured under UV illumination. Inset: The schematic illustration of the measured device b IDS–VDS plot of the P-doped ZnO nanowire FETs transistor with platinum electrodes. Lower right inset: Enlarged IDS–VDScurve in dark. Upper left inset: SEM image of a typical device c NBE of pure and P-doped ZnO nanowires at 10 K. Inset: enlarged part of the peaks around 3.31 eV for P-doped ZnO nanowires d Temperature-dependent PL spectra of P-doped ZnO nanowires with the evolution of two separate peaks around 3.31 eV.

Mentions: To investigate the doping mechanism of P incorporated into the P-doped ZnO nanowires, back-gate field-effect transistors (FETs) measurements were conducted (inset of Figure 3a). Silicon (n±Si) substrates covered by a 300 nm SiO2 layer served as the back-gate and dielectric gate oxide, respectively. Single P-doped ZnO nanowire was dispersed on the substrates. A layer of 20 nm Ni and 80 nm Au was deposited on the two ends of the nanowire as the contact by e-beam lithography and sputtering. The upper left inset of Figure 3b shows a typical image of a single P-doped ZnO nanowire FET. We fabricated twenty FETs in all and found that the as-grown P-doped ZnO nanowires are high resistance. The resistance was so large that the current between drain and source (IDS) could not be modulated by gate voltage (VG), and we could not make sure whether the high resistance came from the nanowire itself. To rule out the other factors that may contribute to the high resistance observed in the P-doped nanowires, we measured the device under UV illumination. IDS as a function of voltage between drain and source (VDS) under different gate voltages (VG) was plotted in Figure 3a, where the gate voltages modulated the current through the nanowire obviously. Thus, we made sure that there was no problem with our measurement process. The presence of the intersection between IDS at VG = 0 V and VG = 20 V is due to the weak modulation of small VG on weak IDS. To further rule out the effect of contact resistance on the measurements, we fabricated platinum electrode at two ends of ZnO nanowire by focused ion beam (FIB)-induced deposition technique, which have previously been proven to be ohmic contact with ZnO [22]. Then, we measured the device in dark and under UV illumination (see Figure 3b), respectively. We can see that the IDS is really weak in dark and the resistance is estimated to be ~104 Ωcm. However, the nanowire forms ohmic contact with the platinum electrode and the contact resistance is not the cause of the high resistance observed above. The IDS is not perfect linear due to low carrier concentration of as-grown nanowire in dark. As concluded from the above discussions, we believe that the nanowires are high resistive. However, we cannot determine the conductive type of our P-doped ZnO nanowires in dark according to the measurements under UV illumination due to the effect of photo-generated carriers [23].


A Novel Way for Synthesizing Phosphorus-Doped Zno Nanowires
a IDS–VDS plots of P-doped ZnO nanowire FETs measured under UV illumination. Inset: The schematic illustration of the measured device b IDS–VDS plot of the P-doped ZnO nanowire FETs transistor with platinum electrodes. Lower right inset: Enlarged IDS–VDScurve in dark. Upper left inset: SEM image of a typical device c NBE of pure and P-doped ZnO nanowires at 10 K. Inset: enlarged part of the peaks around 3.31 eV for P-doped ZnO nanowires d Temperature-dependent PL spectra of P-doped ZnO nanowires with the evolution of two separate peaks around 3.31 eV.
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Figure 3: a IDS–VDS plots of P-doped ZnO nanowire FETs measured under UV illumination. Inset: The schematic illustration of the measured device b IDS–VDS plot of the P-doped ZnO nanowire FETs transistor with platinum electrodes. Lower right inset: Enlarged IDS–VDScurve in dark. Upper left inset: SEM image of a typical device c NBE of pure and P-doped ZnO nanowires at 10 K. Inset: enlarged part of the peaks around 3.31 eV for P-doped ZnO nanowires d Temperature-dependent PL spectra of P-doped ZnO nanowires with the evolution of two separate peaks around 3.31 eV.
Mentions: To investigate the doping mechanism of P incorporated into the P-doped ZnO nanowires, back-gate field-effect transistors (FETs) measurements were conducted (inset of Figure 3a). Silicon (n±Si) substrates covered by a 300 nm SiO2 layer served as the back-gate and dielectric gate oxide, respectively. Single P-doped ZnO nanowire was dispersed on the substrates. A layer of 20 nm Ni and 80 nm Au was deposited on the two ends of the nanowire as the contact by e-beam lithography and sputtering. The upper left inset of Figure 3b shows a typical image of a single P-doped ZnO nanowire FET. We fabricated twenty FETs in all and found that the as-grown P-doped ZnO nanowires are high resistance. The resistance was so large that the current between drain and source (IDS) could not be modulated by gate voltage (VG), and we could not make sure whether the high resistance came from the nanowire itself. To rule out the other factors that may contribute to the high resistance observed in the P-doped nanowires, we measured the device under UV illumination. IDS as a function of voltage between drain and source (VDS) under different gate voltages (VG) was plotted in Figure 3a, where the gate voltages modulated the current through the nanowire obviously. Thus, we made sure that there was no problem with our measurement process. The presence of the intersection between IDS at VG = 0 V and VG = 20 V is due to the weak modulation of small VG on weak IDS. To further rule out the effect of contact resistance on the measurements, we fabricated platinum electrode at two ends of ZnO nanowire by focused ion beam (FIB)-induced deposition technique, which have previously been proven to be ohmic contact with ZnO [22]. Then, we measured the device in dark and under UV illumination (see Figure 3b), respectively. We can see that the IDS is really weak in dark and the resistance is estimated to be ~104 Ωcm. However, the nanowire forms ohmic contact with the platinum electrode and the contact resistance is not the cause of the high resistance observed above. The IDS is not perfect linear due to low carrier concentration of as-grown nanowire in dark. As concluded from the above discussions, we believe that the nanowires are high resistive. However, we cannot determine the conductive type of our P-doped ZnO nanowires in dark according to the measurements under UV illumination due to the effect of photo-generated carriers [23].

View Article: PubMed Central - HTML - PubMed

ABSTRACT

We developed a novel approach to synthesize phosphorus (P)-doped ZnO nanowires by directly decomposing zinc phosphate powder. The samples were demonstrated to be P-doped ZnO nanowires by using scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction spectra, X-ray photoelectron spectroscopy, energy dispersive spectrum, Raman spectra and photoluminescence measurements. The chemical state of P was investigated by electron energy loss spectroscopy (EELS) analyses in individual ZnO nanowires. P was found to substitute at oxygen sites (PO), with the presence of anti-site P on Zn sites (PZn). P-doped ZnO nanowires were high resistance and the related P-doping mechanism was discussed by combining EELS results with electrical measurements, structure characterization and photoluminescence measurements. Our method provides an efficient way of synthesizing P-doped ZnO nanowires and the results help to understand the P-doping mechanism.

No MeSH data available.