Niobium and vacuum deposition of intermetallic compounds of silver nanoparticles

Many of the elements of the periodic table are metals. The actual metal materials used are often not these pure metals, but most of them are Alloy 131 because the alloys usually have better performance. Therefore, people have been making unremitting efforts to find excellent alloy materials. It has been found that the addition of appropriate amounts of rare earth elements in many industrial materials can serve to improve performance and develop new materials. This has been quite successful in practice. 47. The beneficial effects of rare earth elements are usually always associated with their lively chemical properties. . The process of forming various alloys or compounds by interacting with other elements improves the properties of the matrix material. For example, in the T-44Al alloy added 0.15% of rare earth yttrium, yttrium through the alloying with titanium and aluminum, the alloy can be greatly improved at room temperature 18; adding rare earth in steel, rare earth and sulfur and other impurities formed Can remove steel slag, can be used to purify steel, improve the performance of the role of 1451. Recent research shows that 91, in the metal nanoparticle / dielectric composite photo-doped Ag-BgO system doped rare earth can be refined silver nanoparticles and improve the photo-emission The role of the performance, and that the interaction between the rare earth and silver has an effect on the silver nanoparticles, but the specific mechanism is not yet clear. If it can be found out that the rare earth and silver interact with each other to form an alloy during the preparation of the thin film, the explanation of the mechanism of the role of the rare earth in the Ag-Ba3 thin film system will be of great benefit, and it may be applied to the rare earth metal nanoparticle dielectric composite. The theoretical work of the photovoltaic film system provides new ideas. This article studied this.

2. Possibility analysis Alloys are metal-like substances composed of two or more metal elements, or metal elements and non-metal elements. The alloy has two phases or an aggregate state. One is a solid solution in which the proportion relationship among the constituents can be changed. One is an intermediate phase in which the atomic percentage of each constituent element can be represented by a chemical formula, that is, an intermetallic compound, but this chemical formula Generally does not comply with the law of chemical prices. This is due to the fact that the interphase atoms are not generally bonded by simple ionic bonds and covalent bonds, but metal bonds and their mixtures 1101. The alloy forms a solid solution or an intermetallic compound during the formation, according to the Hume-Rothery rule 1U21. It is related to two factors: atomic size factor, chemical affinity factor, and electron concentration factor. If the alloy tends to form a stable intermetallic compound, the solubility of the solute in the primary solid solution is limited, the greater the tendency to form an intermetallic compound, the smaller the solid solubility limit. Conversely, the smaller the solid solubility, the more marked the tendency to form intermetallic compounds.

For atomic size factors, when two metals with different atomic radii form a solid solution, the crystal lattice needs to be distorted, and the larger the difference in size of the two atoms, the more unfavorable the formation of a solid solution. The Hume-Rothery rule states that if the difference in the radius of two metal atoms exceeds 15%, it is difficult to form a solid solution. When ra and rb denote the radiuses of the two atoms of the solvent and the solute, respectively, the atomic size factor that forms the intermetallic compound can be expressed as a chemical affinity factor that is marked by the magnitude of the electronegativity of the two elements. If the two elements that make up the alloy have a large difference in electronegativity, they tend to form a stable intermetallic compound. The greater the difference in the negative charge between the two elements, the more stable the intermetallic compound formed and the limit of solid solubility. The smaller. Daiken and Guny proposed a method 1131 for estimating the mutual solubility of various metals. They use the atomic radius as the abscissa and the electronegativity as the ordinate to make the representative points of each metal. The ellipse is centered on the representative point of the solvent metal. The difference in relative atomic radius on the horizontal axis is 15% The difference in electronegativity on the vertical axis is 4 When the metal in the ellipse is used as a solute, there can be a certain degree of solid solubility, and those outside the ellipse can not be dissolved To the solvent metal. Waben et al. collected data comparing the solid solubility of 1455 alloy systems, confirming that 75% of the systems are consistent with Darken-Gurry's predicted results, especially very successful for rare earth metals 1141. Thus the formation of stable intermetallic compounds is negatively charged. The criterion can be expressed as follows: If the atomic size factor and the chemical affinity factor are both favorable for solute dissolution, ie the values ​​of both are small, then the solid solution limit will mainly depend on the electron concentration factor. The electron concentration is defined as the ratio of the number of valence electrons to the number of atoms, that is, for silver and yttrium binary systems, the enthalpy and silver atomic radii, ie, the enthalpy and silver atomic radii, respectively, differ by 30%, satisfying the atomic size of the formation of intermetallic compounds. according to. The negative neodymium and silver charge densities are 1.1 and 1.931151, respectively. From equation (2), the silver and rhodium binary system also satisfies the electronegativity criterion for the formation of stable intermetallic compounds. Therefore, the tendency of intermetallic compounds to form between the rare earth niobium and silver is large. In fact, as early as the 1960s, people have already confirmed the existence of silver and antimony intermetallic compounds, and studied their composition and structure. 116 This may be because no suitable use of silver and antimony metal compounds has been found. Did not draw wide attention. Some research results have shown that 117, there are AgLaAg2LaAgnLaw, Ag5La and other four forms of silver and antimony intermetallic compounds. See the phase diagram of the binary system of silver and germanium.

Intermetallic compounds are usually formed in high-temperature furnaces under certain equilibrium conditions. Sufficient rigorous full engagement is the basic condition. It is not obvious whether or not an intermetallic compound can be formed under vacuum deposition conditions. This can be analyzed as follows: In the vacuum evaporation, the metal source material is heated to the molten state and vaporized to escape, which is similar to the high-temperature melting state in the high-temperature furnace. It has also been reported 118 that studies using mass analyzers and spectroscopic analysis have shown that almost all metals escape in the form of single atoms during vacuum evaporation. These atoms are incident on the deposition substrate in a vacuum during an adiabatic flight, and therefore must be kept in an overheated state when they escape. When a single atom or atom group migrates, collides, and combines at the surface of the substrate, the degree of fusion is also self-evident due to the fusion of the atom and the size of the atom group, and the atomic group having a single atom or a large specific surface area is also known. The form of collision with other atoms or atom groups, its chemical activity is much larger than the bulk. Therefore, the basic conditions for forming intermetallic compounds under vacuum evaporation deposition conditions are available.

3. X-ray photoelectron spectroscopy experiments and analysis It is known that the inner layer electrons in an atom are affected by the nucleus coulombic force and other electron repulsive forces outside the nucleus. Any change in the charge distribution outside the nucleus will affect the shielding effect on the inner electron. When the electron density of the outer layer is reduced, the shielding effect is weakened, and the binding energy of the inner layer electrons is large, whereas the binding energy is reduced. When the chemical environment around the atom changes, the charge distribution outside the atomic nucleus will change and the binding energy of the inner electrons will change accordingly. This is the chemical shift phenomenon. The internal electronic binding energy can be seen on the X-ray photoelectron spectrum. Peak shifts. If an intermetallic compound is formed between silver and a rare-earth ytterbium under vacuum deposition conditions, the chemical environment surrounding the silver atom will change with the spectral peak of the electron binding energy of the simple silver layer. To verify the interaction between rare earth yttrium and silver, X-ray photoelectron spectroscopy (X-ray photoelectron spectroscopy) was performed on a rro conductive glass substrate by vacuum evaporation of yttrium and silver.

The sample was prepared in an oil-free metal vacuum system consisting of a mechanical pump, a molecular pump for pre-pumping, and a sputter ion pump as the main pump. The working vacuum was 2×15 Pa. The sample was used as a control in order to facilitate the analysis of the effect of rare earth on the silver nanoparticles. That is, at the same time, two silver nano-particles samples are prepared. Under the same conditions of vapor deposition of silver nanoparticles, some of the samples are pre-evaporated to deposit some rare-earth yttrium. The volume ratio of rare-earth antimony to silver is about 1:3. The deposition rate of evaporative deposition of silver and germanium is about 0.2nm/s, the size of silver nanoparticles formed is 20-30nm, and the average particle size of silver and niobium alloy particles is 10nm. Samples are sent to X-ray photoelectron spectroscopy. The analyzer is a 3d orbital binding energy peak of a pure silver sample processed by Origin software. The instrumental error is taken into consideration and the contaminating Cls binding energy is at a value of 2848eV. The silver 3d5/peak is 368. Origin software smooths and pre-evaporates the rare earth. The silver 3d orbital of the hafnium combines energy peaks. It can be seen that each original peak splits into three sub-peaks. After considering the instrument error and correcting with the contaminated Cls binding energy of 2848 eV, the 3d5/peak splits are a-367.6 eV, b-368.7 eV, and c-3699 eV III. Peaks. These three peaks are all different from the pure silver 3d5/peak value. The main peak b-368. 7eV is 0.5eV higher than the standard silver peak. The standard peak similar to this peak is basically silver. There are no silver and antimony metals in the various alignment data. Inter-compound data, but the similarity of intermetallic compounds and the similarity of rare earths, it is reasonable to point out that the 7eV peak is the peak of silver and ytterbium intermetallic compounds. The c-9eV peak may be a shake-up satellite peak because silver may lose 3d orbital electrons during the formation of silver and tantalum intermetallic compounds to become an open shell system, or it may be displaced by an atomic cluster core layer ( The CCS effect was formed because of the presence of clusters of particles less than 1 nm in size during our sample preparation. The a-367.6 eV peak is similar to Ag2O-367. 4eV. As mentioned above, the intermetallic compound is generally not a simple ionic bond and a covalent bond, but a metal bond and a mixture thereof. Therefore, the a-367.6 eV peak may be formed by an ionic or covalent bond component in silver and ytterbium intermetallic compounds, while the b-368.7 eV peak is formed by a metal-bond component in silver and ytterbium intermetallic compounds. X-ray photoelectron spectroscopy analysis results show that under the vacuum deposition conditions, intermetallic compounds are indeed formed between the rare earth niobium and silver, the specific form of which is based on the silver and gallium ratio of our sample and the phase diagram of the binary system of silver and rhenium. It may be Ag2La or AgsLaw, or a mixture thereof.

The binding energy BEf of the inner layer energy level based on the Fermi energy level is added to the chemical potential of the electrons, ie, the binding energy BEf of the inner layer energy can be expressed as the change in the binding energy of the inner layer energy level when the metal forms an alloy. The Fermi level is measured as a benchmark and can be expressed as 1211. With the standard value in the manual. 3 is the change of the electric potential after the blis state hole is the change of the relaxation energy when the charge migrates to the alloy, eV is the charge term of the surrounding atoms in the alloy, and /(AV) is a function of the change of the atomic volume. Unfortunately, most of the items for (6) are still unclear. One is to explain the main source of chemical shifts in the alloy. For simple metals, the calculation of M has progressed to 1221. Watson et al. have tried to calculate the Au-Sn alloy 1211. However, until now, there is still no transition metal. A reliable treatment. So far we cannot explain the X-ray photoelectron spectrum chemical shift of the transition metal alloy accurately. This is particularly true of silver and niobium alloys as a relatively new and less studied alloy, so we can only qualitatively confirm the presence of silver and niobium intermetallic compounds from the 3d orbital binding energy of silver. Further explanation remains to be studied.

4. Conclusion According to the Hume-Rothery rule, the tendency of the formation of intermetallic compounds between silver and niobium was analyzed. According to the conditions of vacuum evaporation deposition, the formation of metal between rare earth niobium and silver was analyzed under vacuum evaporation deposition conditions. The possibility of inter-compounds. The silver yttrium thin films deposited by vacuum evaporation were analyzed by X-ray photoelectron spectroscopy chemical shift method. The results showed that intermetallic compounds were indeed formed between rare earth yttrium and silver under vacuum evaporation deposition conditions. Its specific form may be Ag2La or Ag51La14, or a mixture thereof.

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