Adsorption of Co-Phthalocyanine on Bi2Se3
Manipulating the topological interface by molecular adsorbates: Adsorption of Co-Phthalocyanine on Bi2Se3 Marco Caputo, ,1,2 Mirko Panighel,2,3 Simone Lisi,4 Lama Khalil,1,5 Giovanni Di Santo,2 Evangelos Papalazarou,1 Andrzej Hruban,6 Marcin Konczykowski,7 Lia Krusin-Elbaum,8 Ziya S. Aliev,9 Mahammad B. Babanly,9 Mikhail M. Otrokov,10,11 Antonio Politano,12 Evgueni V. Chulkov,11,13,14,15 Andreś Arnau,11,13,14 Vera Marinova,16 Pranab K. Das,17,18 Jun Fujii,17 Ivana Vobornik,17 Luca Perfetti,7 Aitor Mugarza,3,19 Andrea Goldoni, ,2 and Marino Marsi1 1
Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-
Saclay, 91405 Orsay Cedex, France 2
Laboratory Micro & Nano-Carbon, Elettra - Sincrotrone Trieste S.C.p.A., s.s.14
Km 163.5, 34149 Trieste, Italy 3
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The
Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193 Barcelona, Spain 4
Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 5,
00185 Roma, Italy and Institut Néel, CNRS/UGA UPR2940, 25 Rue des Martyrs BP 166, 38042 Grenoble, France 5
Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-
Yvette Cedex, France 6
Institute of Electronic Materials Technology, 01-919 Warsaw, Poland
7
Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS, CEA, Université
Paris-Saclay, 91128 Palaiseau cedex, France. 8
Department of Physics, The City College of New York, CUNY, New York, New
York 10031, United States 9
Institute of Catalisys and Inorganic Chemistry, Institute of Physics, Azerbaijan
National Academy of Sciences, AZ-1143 , Baku, Azerbaijan 10
Tomsk State University, 634050 Tomsk, Russia
11
Donostia
International
Physics
Center
(DIPC),
20018
Donostia-San
Sebastian, Spain 12
Department of Physics, University of Calabria, via ponte Bucci 31/C, 87036
Rende (CS), Italy 13
Department of Materials Physics, University of the Basque Country UPV/EHU,
20018 Donostia-San Sebastian, Spain 14
Centro de Física de Materiales (CFM), Materials Physics Center (MPC),
Centro Mixto CSIC—UPV /EHU, 20018 Donostia-San Sebastian, Spain 15
Saint Petersburg State University, 198504 Saint Petersburg, Russia
16
Institute of Optical Materials and Technologies, “Acad. G. Bonchev” Str 109,
Sofia, Bulgaria 17
Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science
Park, s.s.14, Km 163.5, 34149 Trieste, Italy 18
International Centre for Theoretical Physics, Strada Costiera 11, 34100
Trieste, Italy 19
ICREA - Instituciò Catalana de Recerca i Estudis Avançats, Lluis Companys
23, 08010 Barcelona, Spain *[email protected], [email protected]
ARPES at 55 eV has been performed in the APE beamline of Elettra synchrotron in Trieste. The beamline is divided in two branches connected by a UHV transfer system: the low energy branch was used to perform ARPES measurements, while on the high energy branch we acquired core-level data to estimate the molecular coverage. Single crystalline ingots of Bi2Se3 were grown from melt by the Bridgman method. At the beginning of the experiment XPS has been used to check the effective cleanness of the cleaved Bi2Se3 surface, controlling that no traces of oxygen, carbon, and nitrogen were present (figure S1).
Figure S1: XPS survey spectrum of the pristine surface. Vertical dashed bars represent the expected binding energy of O1s (531 eV), N1s (398 eV), C1s (285 eV): no peaks are present at those energies. All XPS spectra has been acquired with hν=690 eV.
After that molecules (Sigma-Aldrich, purity 97%) were evaporated from a welloutgassed hand-made tantalum crucible keeping the sample at room temperature. XPS has been used to control the molecular coverage once a layer-by-layer growth for the first monolayer has been checked by STM. The change in the Bi 4f peak intensity has been used to check the thickness of the molecular overlayer, defining 3 Å of thickness one monlayer. The intensity I of the Bi 4f peak of the surface covered by an overlayer of thickness d is related to the intensity I0 of the same peak of the pristine surface and to the universal inelastic electron mean free path λ(Ek) (with Ek the kinetic energy of the emitted electrons) by the Lambert-Beer formula I = I0 e
d
. Reversing this formula and using λ(530
eV)=1nm±10% we obtained the value for d used in the main text. Figure S2 shows the result of this analysis.
Figure S2: Bi 4f peaks upon CoPc adsorption (left) and their intensity dependence in function of the evaporation time (black circles - right). Red marks are the calculated coverage.
ARPES data were collected exciting the sample with a 55 eV p-polarized light, and collecting the outcoming electrons with a Scienta R4000 hemispherical electron analyser. The overall energy resolution is 25 meV. All measurements were performed at 77 K. Every measure shown in the main article for CoPc/Bi2Se3 has been performed on the same sample and the overall experiment took 48h. The disappearance of the surface states at coverage of 1 ML has been checked on a freshly prepared sample (figure S3), with substantially the same results of what shown in the main article.
Binding Energy (eV)
0.0
-0.2
-0.4
-0.6
-0.8
-1.0 -0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
-1
k|| (Å )
Figure S3: Freshly prepared 1ML CoPc/Bi2Se3. Even if blurrier than the image presented in the main article, the disappearance of the topological protected states is still evident.
The same experiment reported in the main text has been performed also with metal free phthalocyanine in order to decouple the effect of the organic part form the metal centre. The effects of metal-free molecules adsorption on Bi2Se3 surface states is summarized in Figure S4. Panel b) of figure S4 shows clearly that 1 ML of simple organic molecules does not affect the topologically protected surface states, and, moreover, that surface states are still discernible even under 3 ML of 2H-Pc (panel c).
a)
b) 0.0
Binding energy [eV]
Binding energy [eV]
0.0
-0.5
-1.0
-1.5
-0.5
-1.0
-1.5
Pristine Bi2Se3
-0.3 -0.2 -0.1
0.0
0.1
0.2
0.3
1 ML 2H-Pc/Bi2Se3
-0.3 -0.2 -0.1
-1
0.2
0.3
k|| [Å ]
c)
d)
Normalized intensity
0.0
Binding Energy [eV]
0.1
-1
k|| [Å ]
-0.5
-1.0
-1.5
0.0
Pristine 1 ML 2H-Pc 3 ML 2H-Pc
3 ML 2H-Pc/Bi2Se3
-0.3 -0.2 -0.1
0.0
0.1
0.2
0.3
-1
k|| [Å ]
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
-1
k|| [Å ]
Figure S4: Effect of 2H-Pc adsorption on the band structure of Bi2Se3 (panels a-c). Panel d shows momentum distribution curves integrated in the interval 0-0.08 eV.
STM topography shown in Figure S5 indicates indeed that also 2H-Pc arrange in a self assembled monolayer on the Bi2Se3 surface.
Figure S5: Topography image of a monolayer of 2H-Pc on Bi2Se3
The persistence of topologically protected states under 2H-Pc adsorption ensures that their vanishing upon CoPc adsorption is an effect induced by the cobalt molecular centre. Experiment at 6.28 eV has been performed in the FemtoARPES setup. The fourth harmonic of a Ti:Sapphire laser system delivers 80 fs pulses at a wavelength of 195 nm with variable polarization. If not stated otherwise all the images are acquired using s polarization in order to enhance the Dirac cone feature. A Specs Phoibos 150 hemispheric analyser equipped with a 2D-CCD camera has been used to collect the photoemitted electrons. Molecular coverage has been measured using the same procedure we used on the APE beamline. In this case, however, we checked the attenuation of the bulk conduction band acquired with HeI line (21.22 eV) coming from a microwave-excited He lamp. STM measurements were carried out by using a Createc UHV LT-STM system, at a base pressure lower than 8x10-11 mbar. The bias voltage of the tunnelling parameters refers to the sample. The images were recorded in constant current mode with a chemically etched W tip.
Laboratoire de Physique des Solides, CNRS, Univ. Paris-Sud, Université Paris-
Saclay, 91405 Orsay Cedex, France 2
Laboratory Micro & Nano-Carbon, Elettra - Sincrotrone Trieste S.C.p.A., s.s.14
Km 163.5, 34149 Trieste, Italy 3
Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and The
Barcelona Institute of Science and Technology, Campus UAB, Bellaterra, 08193 Barcelona, Spain 4
Dipartimento di Fisica, Università di Roma La Sapienza, Piazzale A. Moro 5,
00185 Roma, Italy and Institut Néel, CNRS/UGA UPR2940, 25 Rue des Martyrs BP 166, 38042 Grenoble, France 5
Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, BP48, 91192 Gif-sur-
Yvette Cedex, France 6
Institute of Electronic Materials Technology, 01-919 Warsaw, Poland
7
Laboratoire des Solides Irradiés, Ecole Polytechnique, CNRS, CEA, Université
Paris-Saclay, 91128 Palaiseau cedex, France. 8
Department of Physics, The City College of New York, CUNY, New York, New
York 10031, United States 9
Institute of Catalisys and Inorganic Chemistry, Institute of Physics, Azerbaijan
National Academy of Sciences, AZ-1143 , Baku, Azerbaijan 10
Tomsk State University, 634050 Tomsk, Russia
11
Donostia
International
Physics
Center
(DIPC),
20018
Donostia-San
Sebastian, Spain 12
Department of Physics, University of Calabria, via ponte Bucci 31/C, 87036
Rende (CS), Italy 13
Department of Materials Physics, University of the Basque Country UPV/EHU,
20018 Donostia-San Sebastian, Spain 14
Centro de Física de Materiales (CFM), Materials Physics Center (MPC),
Centro Mixto CSIC—UPV /EHU, 20018 Donostia-San Sebastian, Spain 15
Saint Petersburg State University, 198504 Saint Petersburg, Russia
16
Institute of Optical Materials and Technologies, “Acad. G. Bonchev” Str 109,
Sofia, Bulgaria 17
Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science
Park, s.s.14, Km 163.5, 34149 Trieste, Italy 18
International Centre for Theoretical Physics, Strada Costiera 11, 34100
Trieste, Italy 19
ICREA - Instituciò Catalana de Recerca i Estudis Avançats, Lluis Companys
23, 08010 Barcelona, Spain *[email protected], [email protected]
ARPES at 55 eV has been performed in the APE beamline of Elettra synchrotron in Trieste. The beamline is divided in two branches connected by a UHV transfer system: the low energy branch was used to perform ARPES measurements, while on the high energy branch we acquired core-level data to estimate the molecular coverage. Single crystalline ingots of Bi2Se3 were grown from melt by the Bridgman method. At the beginning of the experiment XPS has been used to check the effective cleanness of the cleaved Bi2Se3 surface, controlling that no traces of oxygen, carbon, and nitrogen were present (figure S1).
Figure S1: XPS survey spectrum of the pristine surface. Vertical dashed bars represent the expected binding energy of O1s (531 eV), N1s (398 eV), C1s (285 eV): no peaks are present at those energies. All XPS spectra has been acquired with hν=690 eV.
After that molecules (Sigma-Aldrich, purity 97%) were evaporated from a welloutgassed hand-made tantalum crucible keeping the sample at room temperature. XPS has been used to control the molecular coverage once a layer-by-layer growth for the first monolayer has been checked by STM. The change in the Bi 4f peak intensity has been used to check the thickness of the molecular overlayer, defining 3 Å of thickness one monlayer. The intensity I of the Bi 4f peak of the surface covered by an overlayer of thickness d is related to the intensity I0 of the same peak of the pristine surface and to the universal inelastic electron mean free path λ(Ek) (with Ek the kinetic energy of the emitted electrons) by the Lambert-Beer formula I = I0 e
d
. Reversing this formula and using λ(530
eV)=1nm±10% we obtained the value for d used in the main text. Figure S2 shows the result of this analysis.
Figure S2: Bi 4f peaks upon CoPc adsorption (left) and their intensity dependence in function of the evaporation time (black circles - right). Red marks are the calculated coverage.
ARPES data were collected exciting the sample with a 55 eV p-polarized light, and collecting the outcoming electrons with a Scienta R4000 hemispherical electron analyser. The overall energy resolution is 25 meV. All measurements were performed at 77 K. Every measure shown in the main article for CoPc/Bi2Se3 has been performed on the same sample and the overall experiment took 48h. The disappearance of the surface states at coverage of 1 ML has been checked on a freshly prepared sample (figure S3), with substantially the same results of what shown in the main article.
Binding Energy (eV)
0.0
-0.2
-0.4
-0.6
-0.8
-1.0 -0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
-1
k|| (Å )
Figure S3: Freshly prepared 1ML CoPc/Bi2Se3. Even if blurrier than the image presented in the main article, the disappearance of the topological protected states is still evident.
The same experiment reported in the main text has been performed also with metal free phthalocyanine in order to decouple the effect of the organic part form the metal centre. The effects of metal-free molecules adsorption on Bi2Se3 surface states is summarized in Figure S4. Panel b) of figure S4 shows clearly that 1 ML of simple organic molecules does not affect the topologically protected surface states, and, moreover, that surface states are still discernible even under 3 ML of 2H-Pc (panel c).
a)
b) 0.0
Binding energy [eV]
Binding energy [eV]
0.0
-0.5
-1.0
-1.5
-0.5
-1.0
-1.5
Pristine Bi2Se3
-0.3 -0.2 -0.1
0.0
0.1
0.2
0.3
1 ML 2H-Pc/Bi2Se3
-0.3 -0.2 -0.1
-1
0.2
0.3
k|| [Å ]
c)
d)
Normalized intensity
0.0
Binding Energy [eV]
0.1
-1
k|| [Å ]
-0.5
-1.0
-1.5
0.0
Pristine 1 ML 2H-Pc 3 ML 2H-Pc
3 ML 2H-Pc/Bi2Se3
-0.3 -0.2 -0.1
0.0
0.1
0.2
0.3
-1
k|| [Å ]
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
-1
k|| [Å ]
Figure S4: Effect of 2H-Pc adsorption on the band structure of Bi2Se3 (panels a-c). Panel d shows momentum distribution curves integrated in the interval 0-0.08 eV.
STM topography shown in Figure S5 indicates indeed that also 2H-Pc arrange in a self assembled monolayer on the Bi2Se3 surface.
Figure S5: Topography image of a monolayer of 2H-Pc on Bi2Se3
The persistence of topologically protected states under 2H-Pc adsorption ensures that their vanishing upon CoPc adsorption is an effect induced by the cobalt molecular centre. Experiment at 6.28 eV has been performed in the FemtoARPES setup. The fourth harmonic of a Ti:Sapphire laser system delivers 80 fs pulses at a wavelength of 195 nm with variable polarization. If not stated otherwise all the images are acquired using s polarization in order to enhance the Dirac cone feature. A Specs Phoibos 150 hemispheric analyser equipped with a 2D-CCD camera has been used to collect the photoemitted electrons. Molecular coverage has been measured using the same procedure we used on the APE beamline. In this case, however, we checked the attenuation of the bulk conduction band acquired with HeI line (21.22 eV) coming from a microwave-excited He lamp. STM measurements were carried out by using a Createc UHV LT-STM system, at a base pressure lower than 8x10-11 mbar. The bias voltage of the tunnelling parameters refers to the sample. The images were recorded in constant current mode with a chemically etched W tip.
