dihalogenated benzene on si surface - leung.uwaterloo.caleung.uwaterloo.ca/group meetings/2004...
TRANSCRIPT
![Page 1: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/1.jpg)
Dihalogenated benzene on Si surface
Silicon surfacesSelected moleculesMotivationExperiment setupAdsorption model of benzeneExperimental resultsSummaryAcknowledgement
![Page 2: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/2.jpg)
Si surface
dimers
Ideal structure 2x1 reconstruction
![Page 3: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/3.jpg)
Selected Molecules
C-Cl 1.75 ÅC-F 1.35 Å C-Br 1.90 Å
1,2-difluorobenzene 1,2-dichlorobenzene 1,2-dibromobenzene
Bond Strength:
C-F=552 kJ/mol C-Cl= 397kJ/mol C-Br=280 kJ/mol C-H=338 kJ/mol
![Page 4: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/4.jpg)
Motivations
Methyl or ethyl substituted benzene molecules show Methyl or ethyl substituted benzene molecules show different reaction mechanism from benzene on Si(100) different reaction mechanism from benzene on Si(100) 2x1. 2x1. R.J. Hamer, J.V.S.T,18 (2000) 1965, Q. Li, K.T. Leung,R.J. Hamer, J.V.S.T,18 (2000) 1965, Q. Li, K.T. Leung,Surf. Sci, 479 (2001) 69.Surf. Sci, 479 (2001) 69.
Halogenated unsaturated hydrocarbons such as Halogenated unsaturated hydrocarbons such as halogenated ethylene and benzene are potential halogenated ethylene and benzene are potential molecules to functionalize the ordered Si(100)2x1 molecules to functionalize the ordered Si(100)2x1 surface for applications of molecular devices and surface for applications of molecular devices and chemical sensors. chemical sensors. M. Bollani, et al., Applied surface science M. Bollani, et al., Applied surface science 175(2001) 379.175(2001) 379.
Halogenated benzenes are fundamentally interesting for Halogenated benzenes are fundamentally interesting for the study of organic silicon chemistry as a benchmark the study of organic silicon chemistry as a benchmark comparison to halogenated ethylenes on Si(100)2x1 in comparison to halogenated ethylenes on Si(100)2x1 in our previous study. our previous study. X.J. Zhou et al., Surface science letter, X.J. Zhou et al., Surface science letter, 543 (2003) L668543 (2003) L668.
![Page 5: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/5.jpg)
Techniques used for the present experiments:Techniques used for the present experiments:
XX--ray photoelectron spectroscopy (XPS), ray photoelectron spectroscopy (XPS), Temperature programmed desorption (TPD), heating rate= 2 K/S.Temperature programmed desorption (TPD), heating rate= 2 K/S.
TPD
XPS
![Page 6: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/6.jpg)
Taking a look at benzene on Si(100)2x1
0.48 eV 1.14 eV (420 K) 1.68 eV (620 K)
For a first desorption, Ed=RTp[ln υ Tp/β-3.64] , Tp=300K, Ed=0.81 eVSo the first adsorption model do not exist at RT. (Consider =10 13 S -1 )υ
Calculated by Gaussian 98 from a model of Si15H16 cluster at B3LYP/6-31G(d) level
B.Borovsky, M. Krueger, E. Ganz, PRB 57(1998),4270.
![Page 7: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/7.jpg)
C 284.6/ C 286.7=2/1Note: Molecular adsorption
![Page 8: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/8.jpg)
![Page 9: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/9.jpg)
1.02 eV
1.06 eV
1.59 eV
1.68 eV
1.66 eV
1.65 eV
![Page 10: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/10.jpg)
C 284.6/C 286.0=3:1
Note: 28% dissociation
Dissociation ratio isin the range of 8-28%
![Page 11: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/11.jpg)
![Page 12: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/12.jpg)
![Page 13: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/13.jpg)
0.99 eV
1.17 eV
1.49 eV
1.63 eV
1.67 eV
1.81 eV
![Page 14: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/14.jpg)
Dissociative adsorption models
F.Y. Naumkin et al, Surface Science 547 (2003) 335
Dissociative adsorption is thermodynamicallyfavorable, but kinetically there is 0.8 eV activation barrier.
![Page 15: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/15.jpg)
Note: 96 % dissociation
![Page 16: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/16.jpg)
![Page 17: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/17.jpg)
![Page 18: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/18.jpg)
Summary
A transition from molecular adsorption to dissociative adsorption of dihalogenated benzene on Si has been observed.The criteria to govern the adsorption transition is the bonding strength of C-X ( X=F, Cl, Br). Cl and Br atoms are easily attacked by atomic H atoms and replaced, which causes the dissociated ratio not reproducible.Adsorption interface can be used to applications such as chemical sensors.
![Page 19: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/19.jpg)
Acknowledgement
Thanks NSERC for funding the present research.
![Page 20: Dihalogenated benzene on Si surface - leung.uwaterloo.caleung.uwaterloo.ca/Group Meetings/2004 Winter/Xiaojing...Taking a look at benzene on Si(100)2x1 0.48 eV 1.14 eV (420 K) 1.68](https://reader035.vdocument.in/reader035/viewer/2022081601/60f8415421d5aa28794ee007/html5/thumbnails/20.jpg)
265 270 275 280 285 290 29512500
13000
13500
14000
14500
15000
15500
16000
16500
17000
17500R
elat
ive
Inte
nsity
Binding Energy (eV)
30 min atomic H induction