研究目的
Investigating the properties of phosphorus- and boron-doped silicon nanocrystals embedded in silicon oxide and silicon oxynitride matrices to determine the presence of free carriers and the efficiency of conventional impurity doping at the nanoscale.
研究成果
The research concludes that no free carriers are present in P- or B-doped Si NCs embedded in silicon oxide or oxynitride matrices at room temperature, due to factors such as quantum confinement, dielectric confinement, and interstitial dopant incorporation. Field ionization can generate carriers at high electric fields, but doping efficiencies are low. This has significant implications for nanoscale device applications, suggesting alternative doping approaches are needed.
研究不足
The study is limited to low dopant concentrations (0.1–1 atom %) and small Si NC sizes (≤5 nm), which may not represent higher doping levels or larger nanostructures. APT measurements have uncertainties due to artifacts like local magnification effects, and the inability to achieve statistically meaningful APT for very low B-concentrations in SRON. The electrical measurements are influenced by the matrix properties, potentially masking some effects.
1：Experimental Design and Method Selection:
The study compares P- and B-doped Si NCs in silicon oxide (SRO) and silicon oxynitride (SRON) matrices using PECVD for fabrication, followed by annealing and hydrogen passivation. Methods include APT for structural analysis, PL and TT for optical properties, and I-V measurements for electrical properties.
2：Sample Selection and Data Sources:
Samples are superlattices of SiO2 and SRO/SRON deposited on Si and quartz glass substrates, with dopant concentrations in the range of 0.1–1 atom %. Data is sourced from fabricated thin films and measured using various analytical techniques.
3：1–1 atom %. Data is sourced from fabricated thin films and measured using various analytical techniques.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment includes PECVD system, quartz tube furnace, MCs+-SIMS (Cameca IMS-4f), APT (LEAP 4000X Si, Cameca), FIB-SEM (Auriga, Zeiss), PL setup with HeCd laser and LN2-cooled CCD, TT setup with fs laser system (Tsunami, Spitfire, Newport), and I-V measurement system (Agilent B1500A, Cascade M150 Prober). Materials include SiH4, N2O, O2, PH3/Ar, B2H6/SiH4, ultra-pure N2, H2 gas, and Al for contacts.
4：Experimental Procedures and Operational Workflow:
Deposition via PECVD, annealing at 1100–1150°C in N2, hydrogen passivation at 450°C, sample preparation for measurements (e.g., MOS capacitor fabrication), and data collection using SIMS, APT, PL, TT, and I-V techniques with specified parameters for each method.
5：Data Analysis Methods:
Data analysis involves proxigram analysis for APT, fitting of PL and TT curves, integration of transient currents for free carrier density calculation, and comparison of results between doped and undoped samples using statistical methods and software tools like IVAS for APT.
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