Chemical state

About: Chemical state is a research topic. Over the lifetime, 2378 publications have been published within this topic receiving 78183 citations.

Effect of Ferric Nitrate on Semi-Insulating 4H-SiC（0001）Chemical Mechanical Polishing

Abstract: Semi-insulating 4H-SiC(0001) has high hardness and high chemical inertness, making it difficult to obtain high material removal rates during chemical mechanical polishing (CMP). In this paper, the role of chemical additive ferric nitrate in semi-insulating 4H-SiC(0001) CMP with α-alumina as abrasive and KMnO4 as oxidant is discussed. The results showed that 0.5 wt% ferric nitrate can increase the removal rate of semi-insulating 4H-SiC(0001) by 34%, while the semi-insulating 4H-SiC(0001) surface roughness Ra was reduced from 0.123 to 0.110 nm. The key point was that the coefficient of friction of the polishing slurry was effectively reduced, which was beneficial to the ploughing effect of the α-alumina abrasive with vermicular thin section morphology which had the highest removal rate. In addition，the chemical composition of 4H-SiC (0001) corrosion layer was analyzed by X-ray photoelectron spectroscopy under different corrosion conditions. Si 2P spectrum analysis showed that O atoms only attack C atoms to produce Si-C-O structure under acidic conditions, whereas, with the addition of ferric nitrate, O atoms not only attacked C atoms, but also attacked Si atoms to produce softer SiO2 and Si-Ox-Cy structures. The chemical mechanical polishing mechanism of Semi-insulating 4H-SiC (0001) is also given.

Light source with a cooled hollow cathode for excitation of spectra of monolithic dielectric samples

Abstract: In addition to its use in isotopic spectral analysis [i] and high-revolution spectroscopy [2], a discharge in a cooled hollow cathode is used even more for high-resolution spectroscopy in elemental analysis of material [3]. In these experiments samples have been employed which differ widely in their structure, aggregation state, and in the chemical state of the sample. As found from experience with cooled hollow cathodes in steady-state work, the sputtering and spectral excitation of the object analyzed depends significantly on its chemical state [4]. In the analysis of metallic samples, the emission spectrum stabilizes almost immediately after the discharge begins. For the excitation of spectra of samples which are chemical compounds it is usually necessary to run the discharge for at least 30 min in order to obtain a stable emission spectrum intensity.

Room temperature formation of Hf-silicate layer by pulsed laser deposition with Hf-Si-O ternary reaction control

Abstract: We investigated the room temperature growth of HfO2 layers on Si substrates by pulsed laser deposition under ultra-high vacuum conditions. The laser fluence (LF) during HfO2 layer growth was varied as a growth parameter in the experiments. X-ray photoemission spectroscopy (XPS) was used to observe the interface chemical states of the HfO2/Si samples produced by various LFs. The XPS results indicated that an interface Hf-silicate layer formed, even at room temperature, and that the thickness of this layer increased with increasing pulsed LF. Additionally, Hf-Si bonds were increasingly formed at the interface when the LF was more than 2 J/cm2. This bond formation process was related to decomposition of HfO2 to its atomic states of Hf and O by multiphoton photochemical processes for bandgap excitation of the HfO2 polycrystalline target. However, the Hf-Si bond content of the interface Hf-silicate layer is controllable under high LF conditions. The results presented here represent a practical contribution to ...

Chemical State Analysis of Fe Compounds Using Heavy Ion PIXE

Abstract: which are proportional to the square of the projectile charge 2) it can be expected that the use of heavy ion beams will improve the sensitivity of the analysis considerably. The lower limit of detection (LLD) in the PIXE analysis using 70 MeV carbon ions is improved 2-4 times compared to that using proton bombardment for heavier elements 3) . Since chemical change due to chemical state of the elements will be expanded due to multiple ionization, it may be measured with a conventional Si(Li) detector. In the last report, the three parameters, the relative change of an intensity ratio of kβ and kα (Intensity Ratio), a ratio of kβ and kα line width (line width ratio) and an energy difference between k� and kα line (relative energy shift), were measured using 70 MeV carbon ions and 3 MeV protons. Changes in those parameters were corresponds to their chemical state. It shows that PIXE with heavy ions will lead to chemical state analysis with high-sensitivity. Here, the Ar ion beams of 78 MeV are applied to chemical state analysis using PIXE. Probability of multiple ionization for Ar ion beams of 78 MeV is higher than that for C ion beams of 70 MeV, which will increase sensitivity in determining chemical state with high sensitivity.

Radiochemical methods of preparing spectrometric sources for studying the chemical effect on the internal conversion of gamma transitions

Abstract: Radiochemical methods for preparing sources of internal conversion electrons for the γ-transitions of 57mFe (14.4 keV), 129Te (27.77 keV), 127Te (57.60. keV), and 127mTe (88.26 keV) were suggested. The sources are intended for studying the conversion of nuclear transitions on external shells of cobalt and tellurium compounds. The chemical state of these elements is monitored by Mossbauer spectroscopy.