Research on cleaning and treating surface impurities of SERS active gold island membrane by low-temperature plasma equipment

• Categories:Company Dynamics
• Author:Plasma cleaning machine-CRF plasma plasma equipment-plasma surface treatment machine manufacturer-chengfeng intelligent manufacturing
• Origin:
• Time of issue:2021-10-06
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(Summary description)Research on cleaning and treating surface impurities of SERS active gold island membrane by low-temperature plasma equipment: The vacuum evaporation method forms a gold island film with surface-enhanced Raman activity on the surface of the silicon wafer. Raman spectroscopy found that the surface of the gold island film has amorphous carbon contaminants. By comparing the Raman spectra of different cleaning methods of low-temperature plasma equipment, it can be proved that cleaning the gold island film with oxygen plasma can effectively remove impurities on the gold surface, and the surface-enhanced Raman activity of the gold island film does not change significantly before and after cleaning.  Raman spectroscopy can provide various normal vibrational frequencies and related vibrational energy levels inside molecules, and is an effective method for studying the molecular structure of substances. Its great advantage is that there are no special requirements for sample preparation, and the sample can be measured in solution. Surface enhanced Raman spectroscopy (SERS) is an analysis technique that combines Raman spectroscopy and surface enhancement phenomena. The emergence of this low-temperature plasma equipment technology has greatly increased the detection sensitivity of Raman spectroscopy, even reaching the level of single-molecule detection. At present, SERS has been widely used in materials science, surface science, biomedicine and other fields, and it is one of the most sensitive spectroscopy techniques for studying surface/interface reactions. The preparation of a metal surface with nano-scale roughness is the primary condition for obtaining the SERS effect. At present, people mainly carry out SERS research on metal sol, metal island film and roughened metal electrode surface. The preparation method of the metal island film is mainly the vacuum evaporation method of low-temperature plasma equipment. The method has the advantages of accurate control of preparation conditions, relatively simple equipment, and easy operation. One of the main disadvantages is the pollution on the surface of the prepared metal island film. Due to the presence of a small amount of organic impurities in the vacuum chamber of the low-temperature plasma equipment during the preparation process, these impurities tend to be adsorbed on the surface of the substrate, resulting in strong and broad characteristic peaks in the obtained spectrum, which can sometimes seriously interfere with the true signal of the measured molecule. Many researchers have recognized this problem and have made various attempts to remove the surface impurities of the SERS substrate. Use CN~ with strong adsorption capacity to remove the contaminated silver surface layer; use alkanethiol to replace and adsorb the contaminants on the metal surface; select Cl i to remove impurities on the surface of the silver particles; chemical adsorption of iodide ions The impurity removal method of electrochemical oxidation: first use low-temperature plasma equipment plasma cleaning, and then use acetic acid soaking method to remove impurities on the surface of self-assembled gold particles, etc. It can be seen that for different SERS bases and experimental conditions, the methods for removing impurities are also different. The principle of plasma cleaning of oxygen low temperature plasma equipment is to generate carbon dioxide, carbon monoxide and water and other volatile substances through the reaction of oxygen free radicals with organic pollutants on the surface of the substrate, and then the vacuum pump sucks these volatile substances away. A layer of gold island film is vacuum-evaporated on the surface of the silicon wafer. The island membrane has a good surface enhancement effect, and the enhancement factor of the pyridine molecule is 10. The surface contamination of the gold island membrane was removed by oxygen ion cleaning, and the spectrum test showed that the surface enhancement characteristics of the gold island membrane did not change significantly before and after cleaning. Plasma cleaning with oxygen low-temperature plasma equipment can remove most of the amorphous carbon impurities on the surface of the gold island film formed by vacuum evaporation; the cleaned substrate can better retain the SERS activity for other molecules; the SERS signal attenuation is less after cleaning . Therefore, oxygen plasma cleaning is an effective way to remove impurities on the surface of the gold island film.