Organometallic Metals: Surface Reactions
Purpose of the study
The purpose of the study was to evaluate the idea of electron induced surface reactions of organometallic metals. As such, the study was focused on metal hfac2, deposition purification and precursors.
Brief background
Surface analytical techniques are some of the commonly used analytical methods in chemistry. These methods are reliable in that they give precise and accurate results (Qian, Li & Garson, 2015). The surface analytical techniques have been very helpful in analyzing the elementary procedures that are related to the structural post-depositions as well as the electron beam-induced treatments. Electron beam-induced deposition, which is commonly abbreviated as EBID, with respect to precursors of organometallic that are volatile, refers to a lithographic technique that makes use of a single step, is site-selective and based on vacuum. This technique can make and prototype 3-D nanostructures that contain metals using microscopes that do not have resists or masks.
Deposition of several metals is possible using precursors that are designed for use in a number of thermally-engineered processes. An example of such processes is the chemical vapor deposition. These processes are used in ensuring that the EBID deposits are consistent with the specific application. For instance, most electronic applications tend to use Cu, as well as Pt containing precursors such as (hfac) Cu1(vinyltrimethylsilane), and MeCpPtMe3. On the other hand, cobalt or iron containing precursors find use in the creation of magnetic nanostructures.
Evidently, all organmetallic precursors have a central atom on which different organic ligands are attached. The attached ligands are either mono-dentate or multi-dentate. The mono-dentate ligands use a single ligand-metal bond to attach themselves to the central atom of any given molecule. The multi-dentate ligands, on the other hand, use several bonds to attach themselves to the central atom of any particular molecule. Some examples of the multi-dentate ligands include CF3C(O)CHC(O)CF3. According to the article, hfac finds most of the use as a multi-dentate ligand since it has the capability of forming bonding with numerous elements. Most of the commonly used compound in EBID especially in the creation of deposition for integrated circuit is the CUII(hfac)2. The reason for such application is that copper has an electrical resistivity that is much lower when compared to aluminum or silicon.
In spite of the fact that EBID, can create flexible structures, several scientific, technological difficulties tend to hinder EBID from achieving its role in nanofabrication. For example, its application results in contamination, especially due to the presence of carbon within the deposits (Joy, 2006). As such, the presence of contaminants in the deposits affects the chemical and physical properties of the element thereby limiting the various areas of EBID application.
Researcher’s approach
The researchers in the study adopted the UHV surface science approach in examining the EBID process. Studies based on the surface science; especially on the absorption of organmetallic precursors, are suitable since they consider all the complexity of the EBID process as opposed to the use of the gas phase studies. In addition, the surface science studies are suitable in that they act as a link to details from studies on typical electron beam-induced deposition.
Observations
The study observed that after analyzing the evolution within the given regions of F (1s), O(1s), C(1s) and Pt (4t) after the exposure of these regions to electron region, as well as changing the concentration the atom, there were various transformation regimes (Rosenberg, Barclay & Fairbrother, 2014). In addition, before the irradiation, it was evident that position of the Pt (4t) while at peak exhibited a doublet position and 74.3 eV. This indicated the possibility of absorbed PtII (hfac)2 molecules. When the electron dose was changed to ≤1 × 1017 e−/cm2, a broadening effect on the Pt(4f) was evident, which led to an electron voltage of 72.6 and exhibited characteristics of Pt(4f7/2/4f5/2). However, considering an electron dose of ≥1× 1017 e−/cm2, reduced species of platinum dominate the spectral envelope of Pt (4f).
The accomplishment of the researchers
From the study it was evident that the researchers aimed at analyzing surface reactions for a number of metalII(hfac)2 precursors. Thus, the results from the experiment showed that the irradiation of metalII (hfac)2 molecules can result in the alteration of the bond environment and the chemical composition of the element used. The researchers therefore were able to observe that electron doses less than 1 × 1017 e−/cm2 showed the most changes in the atomic concentration and bonding (Rosenberg, Barclay & Fairbrother, 2014). The reasoning behind such results is that the metal species from the metalII(hfac)2 molecule is lost to form a more reduced one. The reduced metal species shows characteristics of a binding energy that is intermediate to the metal atoms in the metalII (hfac)2.
From the foregoing, it can be seen that the article provided a clear information with regard to the electron beam induced deposition. The article clearly indicated that various electron doses are responsible for the difference in structural decomposition of any given element or compound. As such, after the decomposition of the molecule, hydrogen, oxygen, fluorine and carbon in the irradiated molecule are lost in the form of H2 (g), F-(g), CO (g)/CO2 (g). Such results explain the formation of the reduced form of the metal species.
Reference List
Joy, D. (2006). What EBID can tell us about contamination? Microscopic Microanal, 12(2), 1660-1661.
Qian, G., Li, Y., & Garson, A. (2015). Applications of surface analytical techniques in Earth Sciences. Surface Science Reports, 70(1), 86-133.
Rosenberg, S., Barclay, M., & Fairbrother, D. (2014). Electron induced surface reactions of organometallic metal (hfac) 2 precursors and deposit purification. ACS Applied Material Interfaces, 6(11), 8590-8601.