Experimental determination of surface thermal expansion and electron-phononcoupling constant of 1T-PtTe2

Gloria Anemone,1, 2 Manuela Garnica,2 Marilena Zappia,3 Pablo Casado Aguilar,1, 2 Amjad

Al Taleb,2 Chia-Nung Kuo,4 Chin Shan Lue,4 Antonio Politano,5, 6 Giorgio Benedek,7, 8

Amadeo L. Vazquez de Parga,1, 2, 9, 10 Rodolfo Miranda,1, 2, 9, 10 and Daniel Farıas1, 9, 10

1Departamento de Fısica de la Materia Condensada,Universidad Autonoma de Madrid, 28049 Madrid, Spain

2Instituto Madrileno de Estudios Avanzados en Nanociencia (IMDEA-Nanociencia), 28049 Madrid, Spain3Dipartimento di Fisica,Universita della Calabria, via ponte Bucci 31/C 87036 Rende (Cs), Italy

4Department of Physics, National Cheng Kung University, 1 Ta-Hsueh Road, 70101 Tainan, Taiwan5Dipartimento di Scienze Fisiche e Chimiche (DSFC),

Universita degli Studi dell’Aquila, Via Vetoio 10, I-67100 L’Aquila, Italy6CNR-IMM Istituto per la Microelettronica e Microsistemi, VIII strada 5, I-95121 Catania, Italy

7Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, Via Roberto Cozzi 55, 20125 Milano, Italy8Donostia International Physics Center (DIPC), University of the Basque Country (EHU-UPV),

Paseo Manuel de Lardizabal 4, 20018 Donostia/San Sebastian, Spain9Instituto ”Nicolas Cabrera”, Universidad Autonoma de Madrid, 28049 Madrid, Spain

10Condensed Matter Physics Center (IFIMAC), Universidad Autonoma de Madrid, 28049 Madrid, Spain(Dated: October 15, 2019)

I. X-RAY DIFFRACTION

PtTe2 crystallizes in the centrosymmetric CdI2-type triagonal (1T) structure with space group P3m1 where six Teatoms form an octahedron around one Pt atom forming a van der Waals stacking Te-Pt-Te layers. Figures 1 showsthe Laue diffraction and the x-ray diffraction (XRD) patterns where only sharp diffraction peaks are observed. Theextracted lattice parameters are a = 4.0065A and c = 5.1897A.

10 20 30 40 50 60 70 80

(023

)(1

21)(0

04)

(113

)

(202

)(0

22)

(103

)(021

)(2

01)

(003

)(1

11)(1

10)

(102

)(0

12)

(002

)(0

11)

(100

)

(001

)

2 (degree)

Inte

nsity

(arb

. uni

ts)

PtTe2a) b)

FIG. 1: (a) Laue diffraction (b) XRD from crushed crystals of PtTe2. The inset shows a picture of the crystal.

II. STM MEASUREMENTS

After cleaving in air, the PtTe2 sample was transferred quickly to our Low Temperature STM for subsequentmeasurements. Large STM image at 4.6K of the crystal shows a quite flat surface with the presence of some localizeimpurities, see Fig. 2.

2

FIG. 2: Large STM images of the PtTe2 surface after cleaving the sample in air and introducing it in the UHV system. Imagewas taken at 4.6K with Vs= 1 V, I = 0.2 nA parameters. The scale bar dispayed is 50 nm.

Figure 3 shows a four zoom-in STM images revealing the presence of different defect types in PtTe2 surface. Thesechalocogenide vacancy defects are in accordance with the observations recently reported for a broad range of TMDsmaterials, such as MoS2 [4] and PtSe2 [3].

FIG. 3: High-resolution STM images of typical defects in the PtTe2 surface. (a) (Vs= 10 mV, I = 3 nA). (b) (Vs= 20 mV, I= 2.8 nA).(c) (Vs= 10 mV, I = 3 nA). (d) (Vs= 20 mV, I = 2.8 nA). The scale bar displayed is 0.5 nm.

III. THERMAL EXPANSION

Figure 4 presents angular distributions of He atoms scattered from PtTe2 surface as a function of sample tem-perature from 100 to 550 K along the high-symmetry direction ΓK and with an incident energy Ei = 32.3 meV.The measurements were taken with ERASMO apparatus. Similar set of measurements was performed with TEAMSapparatus, as shown in Fig. 5, for an incident angle θi = 50◦ and an incident energy Ei = 49.5 meV. HAS angular

3

distributions for PtTe2 surface were reported for different surface temperature that range from 90 to 350 K. Thecrystal was aligned along the high-symmetry direction ΓM.

-30 -20 -10 0 10 20 30

i Relative to Specular (deg)

0

5

10

Inte

nsity

(a.u

.)

Ei = 32.3 meV

(0,0)

(-1,-1) (1,1)

100 K

150 K

200 K

250 K

300 K

350K

400 K

450 K

500 K

550 K

FIG. 4: Temperature dependence of diffraction peaks for PtTe2 along ΓK direction.

Figure 6 shows some selected angular distributions of He atoms scattered from graphene on Ni(111) as a functionof surface temperature from 110 to 650 K. The first order diffraction peaks move to smaller angles when the surfacetemperature rises, that is the lattice constant increase with the temperature.

[1] Wang, Q. H., Kalantar-Zadeh, K., Kis, A., Coleman, J. N., and Strano, M. S. (2012). Electronics and optoelectronics oftwo-dimensional transition metal dichalcogenides. Nature nanotechnology, 7(11), 699.

[2] Chhowalla, M., Shin, H. S., Eda, G., Li, L. J., Loh, K. P., and Zhang, H. (2013). The chemistry of two-dimensional layeredtransition metal dichalcogenide nanosheets. Nature chemistry, 5(4), 263.

[3] Zheng, Husong and Choi, Yichul and Baniasadi, Fazel and Hu, Dake and Jiao, Liying and Park, Kyungwha and Tao,Chenggang. (2018). Intrinsic Point Defects in Ultrathin 1T-PtSe2 Layers. arXiv preprint arXiv:1808.04719.

[4] P. Vancso, G.Z. Magda, J. Peto, J-Y. Noh, Y-S. Kim, C. Hwang, L.P. Biro and L. Tapaszto (2016). The intrinsic defectstructure of exfoliated MoS2 single layers revealed by Scanning Tunneling Microscopy. Scientific Reports 6, 29726.

4

50 60 70 80 90 100 110

i+ f (deg)

1

2

3

4

Inte

nsity

(arb

.uni

ts)

MEi = 49.5 meV

i = 50 deg

90 K

155 K

200 K

250 K

300 K

350 K

FIG. 5: Temperature dependence of diffraction peaks for PtTe2 along ΓM direction.

5

-24 0 24

0.1

1

10

100

650 K

a

Inte

nsity

(arb

.uni

ts)

∆θi Relative to Specular (deg)

110 K

FIG. 6: Angular distributions of 21.5 meV He scattered from Gr/Ni(111) at different surface temperatures.