Ultra-Low Scope Unconstrained Carving and Hyperthermal Desorption of Aluminum Chlorides from Cl 2/Al(111).


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Ultra-Low Scope Unconstrained Scratching and Hyperthermal Desorption of Aluminum Chlorides from Cl 2/Al(111) Tyler J. Grassman , Gary C. Poon, and Andrew C. Kummel College of California, San Diego Gordon Research Gatherings: Progress at Surfaces – August 10-15, 2003 1.0 0.9 0.8 1.0
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Ultra-Low Coverage Spontaneous Etching and Hyperthermal Desorption of Aluminum Chlorides from Cl 2/Al(111) Tyler J. Grassman , Gary C. Poon, and Andrew C. Kummel University of California, San Diego Gordon Research Conferences: Dynamics at Surfaces – August 10-15, 2003 1.0 0.9 0.8 1.0 1000 0.7 0.9 900 1.0 800 1000 0.8 0.9 0.6 0.8 700 900 0.7 0.6 600 0.5 800 0.5 500 700 0.4 0.6 0.3 0.4 400 600 0.2 0.5 0.1 300 500 0.0 0.3 0 1 2 3 4 5 200 400 0.4 100 0.2 300 0.3 0 200 0.1 0.2 100 0 0.1 0.0 535 850 1327 0 10 20 30 40 50 60 70 80 90 100 0.0 0 10 20 30 40 50 60 70 80 0.7 0.6 0.7 0.5 0.6 0.4 0.5 0.3 0.4 0.2 0.3 0.1 0.2 0.0 0.1 Abstract DFT: Bonding to Al Adatoms Results 0.0 0.11 0.27 0.65 Non-resounding multiphoton ionization (MPI) and time-of-flight mass spectrometry (TOF-MS) have been utilized to screen the desorption of aluminum chloride (Al x Cl y ) scratch items from the Al(111) surface at 100 K and 500 K amid low-scope (< 5% monolayer) monoenergetic Cl 2 (0.11 eV to 0.65 eV) dosing. The desorption items in this low-scope extent demonstrate transcendently hyperthermal way out speeds under every dosing condition. For instance, with 0.27 eV occurrence Cl 2 , the engraving item was found to have a most-plausible speed of 517 ± 22 m/s at an Al(111) surface temperature of 100 K. This compares to 22 times the normal warm desorption translational vitality for AlCl 3 . Staying likelihood estimations and Al x Cl y engraving rate estimations show scratching even at Cl 2 scopes of under 5% monolayer at surface temperatures between 100 K and 500 K. These test results are steady with a blend of quick time-scale and low Cl surface scope arrangement of aluminum chlorides and the vicinity of actuated aluminum chloride chemisorption states having potential energies over the vacuum level, and are in opposition to the standard high-scope picture of aluminum chloride engraving obliging high surface scope (>1 monolayer) and subsurface Cl dispersion. Thickness practical hypothesis counts yield comes about that are reliable with both our exploratory discoveries and unthinking portrayals. Measured speeds, translational energies, and top to-width proportions for desorbing aluminum chlorides at all episode Cl 2 translational energies and Al(111) surface temperatures considered. Non-reinforced Bonded E (eV) b v p :w v p (m/s) E inc (eV) T s (K) E (eV) a Dose Species AlCl 3 Al 2 Cl 6 612.3 ± 21.2 ― 0.522 ± 0.037 0.65 ± 0.06 Cl 2/He: low c 0.65 100 D E = - 2 eV 0.65 100 Cl 2/He: high d 255.5 ± 9.2 ― 0.092 ± 0.007 0.84 ± 0.08 Cl 2/He 0.65 500 653.1 ± 15.5 0.296 ± 0.014 ― 0.56 ± 0.02 Cl 2/Ne 0.27 100 517.7 ± 22.0 ― 0.378 ± 0.032 0.82 ± 0.03 Cl 2/Ne 0.27 500 552.9 ± 14.2 0.213 ± 0.011 ― 0.76 ± 0.03 0.11 100 460.3 ± 22.3 ― 0.303 ± 0.029 0.69 ± 0.06 unadulterated Cl 2 immaculate Cl 2 0.11 500 533.3 ± 9.8 0.197 ± 0.007 ― 0.71 ± 0.05 Al Cl Al (notice.) DFT piece counts of Cl adsorbates on the Al(111) surface close to an Al adatom show an in number lively inclination for Cl molecules to cling to Al adatoms instead of stay scattered at first glance (out of holding extent). This is liable to be the situation for regrowth islands and step edges, also. The surface response, 3Cl (commercial.) + Al (notice.) → AlCl 3(ad.) , is computationally observed to be around 2 eV thermodynamically ideal. These AlCl 3 adsorbates are likewise likely be exceptionally portable at first glance, as the surface tying potential for the particles (regarding the distinctive conceivable adsorption destinations) was found to have a most extreme groove of just 0.1 eV. a : Translational vitality figured from mass of AlCl 3 scratch item and measured v p b : Translational vitality computed from mass of Al 2 Cl 6 carve item and measured v p c : Total dosing time ≤ 10 sec d : Total dosing time > 10 sec Experimental Methods • Very low Cl 2 flux (~ 2x10 14 cm - 2 sec - 1 ) beat sub-atomic pillar • MPI (210.2 nm) and TOF-MS → photodissociate Al x Cl y , recognize Al + • King & Wells sort staying estimations with QMS • DFT-GGA with Vanderbuilt ultrasoft pseudopotentials and plane-wave premise, 7 ×6ã—1 21 k-point Monkhorst-Pack, 250 eV plane-wave cut-off for Cl/Al(111) adsorbate framework ( V ienna A b-initio S imulation P ackage, VASP) Exit versus Occurrence Velocities/Energies DFT: Bonding on Terraces (a) (c) (T s = 500 K) (T s = 100 K) Experimental Clustered AlCl 3 (warm) AlCl (warm) Dispersed Al 2 Cl 6 (warm) AlCl 3 (warm) AES Mechanical Chopper (7 m s) 535 850 1327 Exit Velocity, v exit (m/s) Exit Velocity, v exit (m/s) Skimmer Ionizer (210.2 nm) QMS Pulsed Nozzle (10Hz) Al(111) Cl 2 Incident Velocity, v inc (m/s) Cl 2 Incident Velocity, v inc (m/s) Collimator TOF-MS (Cl 2/He, Cl 2/Ne immaculate Cl 2 ) LEED (b) (d) Thermal (T s = 500 K) (T s = 100 K) AlCl (exp) AlCl 3 (exp) AlCl 3 (exp) Al 2 Cl 6 (exp) 0.11 0.27 0.65 Exit Energy, E exit (eV) Exit Energy, E exit (eV) DFT piece counts of the Cl/Al(111) adsorbate/patio framework intended to analyze the likelihood of adsorbate grouping don\'t demonstrate a thermodynamic inclination for bunching geometries. In any case, the computations do demonstrate an in number inclination for ontop adsorption destinations, with contrasts altogether energies of - 0.4 to - 0.9 eV contrasted with different locales. Ontop-site Cl adsorbates are additionally found to pull the Al patio particle to which they were reinforced out of the surface plane by 0.4 Å, subsequently likely making them more powerless against assault by other nuclear or atomic adsorbates, and serving to renew nucleation destinations. 1.0 0.9 Cl 2 Incident Energy, E inc (eV) Cl 2 Incident Energy, E inc (eV) 0.8 Etch item leave speeds and energies plotted against episode speeds and energies, separately, for surface temperatures of 100 K and 500 K. The open images (squares, circles, triangles, jewels) speak to exploratory information, while the filled images speak to the normal qualities from an absolutely warm desorption system. The information obviously demonstrates that the engraving items are leaving the surface at hyperthermal speeds. 0.7 Time-of-Flight Distributions 0.6 0.5 0.4 0.3 0.2 Values extricated from trial time-of-flight spectra analyzed against qualities taken from expected warm appropriations (flux-weighted Maxwell-Boltzmann for thickness finder): 0.1 (a) 0.0 (Inc. Cl 2/Ne T s = 100 K) Conclusion Etch Rate Profiles 1.0 0.9 0.8 “most-likely time of flight” 0.7 Normalized Al + Intensity (arb.) (a) (b) 0.6 Observed Al 2 Cl 6 TOF (a) (b) 1.0 Standard Activated Chemisorption Model Activated Chemisorption State Model 0.5 0.9 500 m/s Al 2 Cl 6 part (T s = 100 K) Expected 100 K Al 2 Cl 6 TOF 0.8 0.7 0.4 Energy (arb.) Energy (arb.) 0.6 “most-plausible velocity” 0.5 0.3 0.4 30 60 90 120 150 180 210 240 270 300 0 initiated chemisorption state 0.3 0.2 Time ( m sec) 0.2 0.1 way out active vitality exit motor vitality 0.1 (b) 0.0 Etch Rate (arb.) Etch Rate (arb.) 0 1 2 3 4 5 vacuum level vacuum level (Inc. Cl 2/Ne T s = 500 K) 0.0 “most-likely translational energy” 550 m/s AlCl 3 segment (T s = 500 K) 0 10 20 30 40 50 60 70 80 Begin surface Cl 2 presentation Thermal appropriation ought to display most-presumably speed to width proportion (v p :w) of around 1. A test proportion littler than solidarity shows a more extensive conveyance than would be normal for a simply warm desorption instrument. Start surface Cl 2 presentation chemisorption well chemisorption well Distance From Surface (arb.) Distance From Surface (arb.) Normalized Al + Intensity (arb.) The bizarre desorption wonders saw in this work is reliable with a model comprising of a blend of quick surface agglomeration of Cl and Al x Cl y adsorbates (as found in the engraving rate profiles, and in addition the computational information) and the presence of enacted aluminum chloride chemisorption states, with potential wells over the vacuum level. The enacted chemisorption state model is diagrammed in the figure above (b), and is contrasted and the standard actuated chemisorption show (an) in which the chemisorption well is beneath the vacuum level and desorbing species must surmount an initiation obstruction. Time (sec) Time (sec) Observed AlCl 3 TOF Etch rate profiles of the 0.27 eV occurrence vitality Cl 2 on (a) the 100 K and (b) the 500 K Al(111) surface. The insets are blow-ups of the shaded districts and demonstrate the initial 5 seconds of information. As found in the figures, scratching starts endless supply of the Al(111) surface to the low-flux Cl 2 sub-atomic pillar, at surface scopes of < 5% monolayer. Such results show quick time-scale surface agglomeration of adsorbed Cl particles/atoms and submolecular aluminum chlorides. Expected 500 K AlCl 3 TOF Maxwell-Boltzmann-like time-of-flight dissemination bends for the engraving items from the 0.27 eV occurrence Cl 2 bar on the (a) 100 K and (b) 500 K Al(111) surface. The strong bends demonstrate the tentatively watched desorption dispersion, and the dashed bends demonstrate the normal warm desorption time-of-flight conveyance for the engraving item mass and surface temperature of enthusiasm, as showed in the figures. The most likely time-of-flights are shown by the vertical, single-headed bolts. The full-width half-max of th

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