HfO2 {is a|is really a|is actually a|can be a|is often a|is usually a} high-k material {that is|that’s|which is|that is certainly|that is definitely|that may be} {used|utilized|employed|utilised|applied|made use of} in semiconductor devices. Atomic-level {control|manage|handle} of material processing is {required|needed|necessary|essential|expected} for the fabrication of thin films of high-k {materials|supplies|components} at nanoscale device sizes. Thermal atomic layer etching (ALE) of metal oxides, in which {up to|as much as} {one|1|a single|one particular} monolayer of material {can be|may be|could be|might be|is often|is usually} removed, {can be|may be|could be|might be|is often|is usually} {achieved|accomplished} by sequential self-limiting (SL) fluorination and ligand-exchange reactions at elevated temperatures. First-principles {based|primarily based} atomic-level simulations {using|utilizing|making use of|employing|working with|applying} density functional theory (DFT) can give deep insights {into the|in to the} precursor chemistry {and the|and also the|as well as the|along with the|plus the} reactions that drive the etch of metal oxides. A {previous|prior|earlier|preceding} study examined the hydrogen fluoride (HF) pulse {in the|within the|inside the} {first|initial|very first|1st|initially} step {in the|within the|inside the} thermal ALE {process|procedure|method|approach|course of action} of crystalline HfO2 and ZrO2. This study examines the HF pulse on amorphous HfO2 {using|utilizing|making use of|employing|working with|applying} first-principles simulations. The Natarajan-Elliott {analysis|evaluation}, a thermodynamic methodology is {used|utilized|employed|utilised|applied|made use of} to {compare|evaluate|examine} reaction models representing the self-limiting and spontaneous etch processes taking {place|location|spot} {during|throughout|in the course of|for the duration of|through} an ALE pulse. For the HF pulse on amorphous HfO2, we {found|discovered|identified|located} that thermodynamic barriers impeding spontaneous etching are present at ALE relevant temperatures. HF adsorption calculations {on the|around the} amorphous oxide surface is studied {to understand|to know} the mechanistic {details|particulars|specifics|information|facts} {of the|from the|in the|on the|with the|of your} HF pulse. A HF molecule adsorbs dissociatively by forming Hf-F and O-H bonds. HF coverages ranging from 1.1 ± 0.{3|three} to 18.0 ± 0.{3|three} HF/nm2 are investigated {and a|along with a|as well as a|plus a|and also a|in addition to a} mixture of molecularly and dissociatively adsorbed HF molecules is present at {higher|greater|larger} coverages. A theoretical etch {rate|price} of -0.82 ± 0.02 Å/cycle for amorphous HfO2 was calculated {using|utilizing|making use of|employing|working with|applying} a maximum coverage of 9.0 ± 0.{3|three} Hf-F/nm2. This theoretical etch {rate|price} is {greater|higher} than the theoretical etch {rate|price} for crystalline HfO2 that we previously calculated at -0.61 ± 0.02 Å/cycle. Undercoordinated atoms and void regions in amorphous HfO2 {allows|enables|permits|makes it possible for} for {more|much more|a lot more|far more|additional|extra} binding {sites|websites|web sites|internet sites|web-sites|web pages} {during|throughout|in the course of|for the duration of|through} fluorination whereas crystalline HfO2 {has a|features a|includes a} {limited|restricted} {number of|quantity of|variety of} adsorption {sites|websites|web sites|internet sites|web-sites|web pages}. Fmoc-D-beta-indanylglycine Purity 1394346-20-3 web PMID:26644518
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