(a) 60° tilted view SEM images of crystalline silicon samples treated in CF4 plasma at 200 W (NT-1) and 300 W (NT-2) for a treatment time of 20 min and at 100 W for 60 min (NT-3). (b) Averaged values of the total reflectance vs. the height of the nanostructures. The total reflectance of polished pSi surface has been inserted for comparison.
(a) Semilog plot of the Jdk vs. V curve collected on devices tailored on NT silicon surfaces in Fig. 1. Jdk vs V read out on polished pSi device are shown for comparison. The inset represents a schematics of the device under test. (b) Semilog plot of the Jph vs V curve collected on devices tailored on NT silicon surfaces in Figure 1 evidencing the photovoltaic behavior of the devices. The Jph vs V read out on polished pSi device are shown for comparison.
Correlation of minority carrier lifetimes, as extracted from transient photocurrent decay data, with open circuit voltages resulting from Jph vs V read out. The inset shows a typical result of transient photocurrent decay of minority carrier density generated by the pulsed laser light. Data refer to measurements on Au/NT-1/pSi structures.
Normalized photo-yield spectra calculated from short circuit photocurrent for the Au/NT-X/pSi devices. The normalized photo-yield spectrum of a commercial silicon photodiode is also represented. A significant red shift has been found for nanostructures tailored at 200 W/20 min (NT-1) and 100 W/60 min (NT-3). In the inset, the correlation of maximum photo-yield wavelength with the nanotexturing aspect ratio is represented.
(a) Schottky-Mott plots (1/C2 vs V) calculated from 1 MHz specific capacitance-voltage data collected at reverse bias for Au/NT-X/pSi diodes. The values of the built in potential extracted from Au/pSi diodes have been also indicated. (b) Typical oscillating behavior of flat band capacitance observed at voltage sine wave frequency lower than 1 MHz in Au/NT-X/pSi structures. The data refer to f = 10 kHz. The C-V collected in Au/pSi structures at the same voltage signal frequency is also shown.
(a) Correlation of negatively charged fluorine atom concentrations obtained from XPS data with open circuit voltages and surface potentials. (b) C-V read out for an Au/NT-X/nSi structure obtained under the same plasma conditions of NT-2/pSi structure. An opposite shift in built in potential after texturing is evidenced. In the inset, the oscillating behavior due to nanotexturing has been again observed. The frequency of the sine wave voltage signal (10 kHz) is the same of data in Figure 5(b) on pSi.
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