研究目的
To investigate nitrogen adsorption on Si(100) surfaces using plasma excited NH3 compared to pure NH3, focusing on coverage, species formed, and mechanisms, to understand low-temperature processes for applications like GaN ALD.
研究成果
Plasma excited NH3 achieves higher nitrogen coverage (0.54 ML) at RT compared to pure NH3 (0.13-0.25 ML), with Si2=NH as the major species. Nitridation begins at 550°C for both treatments. The plasma process enhances low-temperature adsorption, which could benefit GaN ALD by enabling lower temperature growth and higher deposition rates.
研究不足
The study is limited to Si(100) surfaces and specific treatment conditions (e.g., 5 min treatment time, temperatures up to 800°C). Potential contamination from chamber walls during plasma process was noted, which could affect results. Optimization could include varying treatment times or using different substrates.
1：Experimental Design and Method Selection:
The study uses in situ IR absorption spectroscopy and ex-situ XPS to analyze nitrogen adsorption on Si(100) surfaces treated with pure and plasma excited NH3 at temperatures from RT to 800°C for 5 minutes. The rationale is to compare adsorption mechanisms and coverage.
2：Sample Selection and Data Sources:
p-type (100)-oriented Si wafers with resistivity 8-10 Ω·cm were used. Samples were cleaned by RCA method and HF dip to remove native oxide, then thermally cleaned in UHV at ~1050°C.
3：List of Experimental Equipment and Materials:
Equipment includes a UHV chamber with base pressure <1.0×10^{-6} Pa, turbo molecular pump, gate valve, gas introduction system, in-situ IR absorption spectroscopy instrument, XPS with MgKα X-ray source, plasma generation system with 13.56 MHz RF power at 30 W, optical emission spectroscopy. Materials include Si wafers, pure NH3 gas, Ar gas (used as carrier for plasma), HF acid.
4：0×10^{-6} Pa, turbo molecular pump, gate valve, gas introduction system, in-situ IR absorption spectroscopy instrument, XPS with MgKα X-ray source, plasma generation system with 56 MHz RF power at 30 W, optical emission spectroscopy. Materials include Si wafers, pure NH3 gas, Ar gas (used as carrier for plasma), HF acid.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: After cleaning, samples were thermally cleaned. Plasma excited NH3 (generated with Ar carrier) or pure NH3 was irradiated for 5 min at constant substrate temperatures. Nitrogen coverage and species were analyzed using XPS and IR spectroscopy. Plasma was characterized by optical emission spectroscopy.
5：Data Analysis Methods:
Nitrogen coverage was calculated from N1s and Si2p photoelectron intensity ratios in XPS, calibrated with Au 4f. Chemical states were evaluated from binding energy shifts. IR spectra were analyzed for hydride species using multiple internal reflection mode.
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