4 th Graduate Summer Institute “Complex Plasmas” RF hollow discharge and its influence on metal nanoclusters Amir Mohammad Ahadi 1 , T.Trottenberg 2 , O.Polonskyi 1 , T.Strunskus 1 , H.Kersten 2 and F.Faupel 1 1 Chair for Multicomponent Materials, CAU-Kiel 2 IEAP, CAU-Kiel 5 August 2014 amah@tf.uni-kiel.de 1
Outline - Motivation - Characterization of RF hollow discharge - Setup - Single and compensated probe - Influence of RF Power on discharge - Effect of pressure - Influence of reactive admixture - Nanoclusters in RF hollow discharge - Effects of nanoclusters on RF plasma - Influence of discharge on cluster deposition - Cluster size evolution - Summary and Outlook 2
Motivation - RF plasmas are used for plasma polymerization, material deposition and … - Clusters: Important role in fabrication of new nanocomposite materials and in adjusting the properties of nanomaterials. F.Faupel et.al, Adv.Eng.Mat, Vol.12, No.12, 1177 (2010) - Due to the symmetric geometry and high ionized discharge, cylindrical hollow discharge is very interesting tool for study. 3
Characterization of RF hollow discharge 4
Setup Schematic drawn of experimental setup. 5
Langmuir probe was installed 12 mm far from top ring electrode ! 6
Single and compensated probe Langmuir probe: P=2 Pa, Ar flow= 115 SCCM Power=10 W 7
Influence of RF power on discharge Evolutions of electron temperature and density by loading power Solid lines are for single probe measurements and dashed lines are for compensated probe measurements. 8
V-I probe e measurem rements ents P=2 Pa Ar flow= 115 SCCM 300 120 89.4 2.4 89.3 280 119 2.2 89.2 260 Discharge Impedance (Ohm) 2.0 Discharge Phase (°) Discharge Voltage(V) Discharge Current (A) 118 89.1 240 89.0 1.8 220 117 88.9 1.6 200 116 88.8 1.4 180 88.7 115 1.2 160 88.6 140 1.0 114 88.5 0 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 16 18 RF Power (W) RF Power (W) By increasing the RF power, the plasma gradually becomes more resistive. 9
Effect of pressure - Growing electron density by increasing argon density. - Decreasing electron temperature due to decreasing mean free path by pressure. 10
All discharge parameters decreased by increasing the pressure, as the consumed power be constant. 11
Influence of oxygen admixture P = 2.00 Pa RF power = 7.00 W E Argon = 15.8 eV Eo xygen = 12.6 eV - Higher ionization energy leads to higher electron temperature . - Molecular excitation and dissociation are additional source in oxygen plasma. K.J.Taylor and G.R. Tynan, J.Vac.Sci.Tech A, 23 (4), 2005 12
Nanoclusters in RF hollow discharge 13
Setup Sample & QCM position Defe felecto tor With th two slits ts 14
Effects of nanoclusters on RF plasma Langmuir probe P=2 Pa With Out cluster Magnetron Power=50 W With all clusters With neutral clusters 9 9 5.0 5.0 4.8 4.8 4.8 8 8 4.6 4.6 7 7 4.4 4.4 4.4 Electron Density (m^-3)*E15 6 6 electron Temp (eV) 4.2 4.2 5 5 4.0 4.0 4.0 3.8 3.8 4 4 3.6 3.6 3.6 3 3 3.4 3.4 2 2 3.2 3.2 3.2 1 1 3.0 3.0 2.8 2.8 2.8 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 RF Power (w) RF Power 15
V-I Probe 300 300 122 122 89.4 89.4 2.4 2.4 89.3 89.3 280 280 121 89.2 89.2 2.2 2.2 260 260 89.1 89.1 Discharge Impedance (Ohm) 120 120 Discharge Phase (°) Discharge Current (A) 2.0 2.0 Discharge Voltage (V) 89.0 89.0 240 240 88.9 88.9 119 1.8 1.8 220 220 88.8 88.8 118 118 88.7 88.7 1.6 1.6 200 200 88.6 88.6 117 1.4 1.4 180 180 88.5 88.5 88.4 88.4 1.2 1.2 116 116 160 160 88.3 88.3 140 140 1.0 1.0 115 88.2 88.2 0 0 2 2 4 4 6 6 8 8 10 10 12 12 14 14 16 16 18 18 0 0 2 2 4 4 6 6 8 8 10 10 12 12 14 14 16 16 18 18 RF Power (W) RF Power (W) Solid lines are for pure plasma (without clusters) and dashed lines are for plasma in presence of cluster beam. 16
Influence of RF Power on cluster beam Spatial distribution of deposition rate at different RF powers 900 RF Power:0 W 800 RF Power:10 W RF Power:2 W 700 600 Deposition Rate (a.u.) 500 400 300 200 100 0 -10 -5 0 5 10 Distance from center of deposition (mm) 17
Magnetro tron Power r = 50 W P M.C. = 2 Pa P GAS = = 200 Pa At higher RF power (higher than 5 w), the nanocluster deposition with and without purification (of neutral clusters) was similar. 18
Cluste ter r size e evoluti tion on DC Power r =100 W P M.C. C. =2 Pa P GAS =2 =200 Pa Cluster er film _ without t RF discharg arge e Cluster er film_ 2 W R RF discharge arge 19
Cluster er film _ 10 W R RF discharge arge Higher energy enhence cluster charging & more acceleration of nanoparticles the cluster size can grow by coalescence of clusters in the volume. 20
Summary -We could successfully setup and characterize a small RF discharge at low pressure and low power for material processing. - At applied conditions, the influence of Ag nanoclusters (were added to the discharge) on discharge parameters was not noticeable. - Not only the spatial distribution, but also the deal of deposited nanoclusters are significantly changed by appling the RF discharge. - Preliminary evaluations show that the size distribution of clusters as well as the clusters mean size are affected by the RF discharge. 21
Next steps (Outlook) - Charging of nanoclusters by RF hollow discharge (In progress). - Using the RF hollow discharge for plasma polymerization. - Combine with other methods (such as magnetron sputtering or GAS ) to produce nanocomposites and also core-shell nanoparticles. . . . 22
Acknowl owledg dgem ements nts - This work has been supported by the German Research Foundation (DFG) SFB TR 24- B13. - We would like to thank Stefan Rehders for the technical construction of the cluster source and hollow cathode and Alexander Hinz for TEM measurements. 23
Kiel - Sailing City 24
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