研究目的
To synthesize nanostructured AlN films using pulsed laser deposition under different conditions and characterize their structural and vibrational properties using XRD, TEM, and Raman spectroscopy, including surface-enhanced Raman scattering (SERS), to demonstrate the feasibility of SERS for characterizing such films.
研究成果
PLD AlN films deposited in vacuum are nanostructured with hexagonal phase and columnar structure, while those in nitrogen ambient are amorphous with nanocrystallites. SERS effectively enhances Raman signals and reveals stress-induced shifts and surface oxidation effects, demonstrating its utility for characterizing nanostructured AlN films for applications in nanoscale electronic devices.
研究不足
The study is preliminary, and SERS may introduce peak broadening and influence from the colloidal silver suspension. The films are thin, leading to weak Raman signals without enhancement. The ambient conditions and pressures used may not cover all possible synthesis parameters, and the focus is on AlN films, limiting generalizability to other materials.
1：Experimental Design and Method Selection:
Pulsed laser deposition (PLD) was used to synthesize AlN thin films on Si substrates under varying conditions of ambient (vacuum or nitrogen gas at different pressures) and laser repetition rates (3 Hz or 10 Hz). The films were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman spectroscopy, including surface-enhanced Raman scattering (SERS) with colloidal silver suspension for signal enhancement.
2：Sample Selection and Data Sources:
Stoichiometric AlN target was ablated using a KrF* excimer laser, and films were deposited on (100)Si substrates heated to 800°C. The number of laser pulses was 20,000 for each film. Data were acquired from XRD patterns, TEM images, and Raman spectra.
3：List of Experimental Equipment and Materials:
Equipment includes a KrF* excimer laser source, Philips X'Pert XRD equipment, Philips CM 20 and JEOL 3010 electron microscopes, HR4000 Raman spectrometer, and materials such as AlN target, Si substrates, AgNO3, sodium citrate, and colloidal silver suspension.
4：Experimental Procedures and Operational Workflow:
Films were deposited by laser ablation with specified parameters. XRD measurements were performed with Cu radiation. TEM samples were prepared by ion thinning after mechanical polishing. For SERS, colloidal silver suspension was applied to the film surface before Raman measurements using a 785 nm laser.
5：Data Analysis Methods:
XRD peak broadening was analyzed using Sherrer's formula to estimate crystallite size. TEM images were used to observe microstructure. Raman spectra were analyzed to identify phonon modes and shifts due to stress.
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