Designing of metallic nanocrystals embedded in non-stoichiometric perovskite nanomaterial and its surface-electronic characteristics

Engineering of novel functional nanocomposite as like as the metallic nanocrystals supported non-stoichiometric perovskite nanomaterial in controlled parameters (size, shape and ratio of chemical characteristics) is a challengeable task. In this context, we present a facile route to fabricate and study its physicochemical property at real time mode in this report. Nanoscale pure Pb crystals surfaced on non-stoichiometric A-site deficient Pb1-xTiO3-y nanoparticle were fabricated when a precursor lead titanate (PbTiO3) nanoparticle was exposed to an electron beam irradiation (EBI) in a transmission electron microscope (TEM) at ambient temperature. In the state of the art, the chemical states and electronic structure of non-irradiated and irradiated PbTiO3 were studied by X-ray photoelectron spectroscopy (XPS). Electron bombardment resulted in a new visible feature at low binding energy in the Pb 4f core level, while Ti 2p and O 1s line shape showed slight changes. The Fermi level of the corresponding materials was determined to be 1.65 ± 0.1 eV and 2.05 ± 0.1 eV above the valence band maximum, respectively. The normal, weakly p-type PTO exhibits peculiar n-type feature after EBI process (The Fermi level moves near to the conduction band). A feasible mechanism is proposed involving the electron-stimulated local bond-breaking phenomenon in PbTiO3.


XRD analysis
. XRD patterns of PbTiO 3 powder calcined at 450 O C temperatures for 1h. The XRD pattern reveals reflection lines corresponding to the expected single phase. The pure PbTiO 3 perovskite phase was clearly observed, which is calcined (450 o C) at below the Curie temperature (490 o C) of the material. The crystal system was represented as tetragonal (space group: P4mm).
All the peaks are well matched with the JCPDS PDF#78-0298 standard data card. There is no evidence of bulk remnant materials and impurities.    five fold multiple twinned particles as commonly observed in the fcc metal nanoparticle. Based on this assumption we derived that the Pb multiple twinned nanoparticle has decahedron shape.

HRTEM analysis
Normally the decahedron composed of the five tetrahedra. In this case, the non isolated particle had shown the two tetrahedra in the structure. The result consists with the earlier study of other fcc metals nanoparticle reported elsewhere.   formation. To be skeptical on PbO evolution from the PTO matrix, we deliberately analysed a newly emerged particle on the surface of the PTO matrix. The EDS spectrum shows that only Pb element presents at 99 at.% (Fig. 5(c)). Moreover the reduction of oxygen around 10 to 20 at.% is observed in this study. These results exhibit step-1 and 2 are not a promising mechanism. TiO 3-y surface from another region. These particles will accumulate at random positions. When the element mapping has been performed on these positions, it turns out that a Pb/ Pb 1-x TiO 3-y mixture is newly formed. Therefore the derived chemical formula is Pb a TiO b (where a>1 and b<3). On the whole, the step-3 mechanism is a possible way to explain the formation of pure lead supported in the cation deficient PTO matrix.  Figure S9. TEM image of electron beam spot, whose diameter is about 50 nm. Figure S10. XPS survey spectra of both the non-irradiated and irradiated PTO

Specimen heating effect:
When a high energy of electron passes through the materials, they create the thermal spikes. The total energy loss of the electron, Where, Q e and Q c are electron excitation and coulomb encounter loss, respectively. These energy loses can be calculated by following equation, (2) Where, constant The electron beam induced temperature increment (ΔT e ) of PTO matrix for time t e seconds is given by, Where D= k t /c v d (k t is the thermal conductivity, c v is specific heat and d is the density), e is a charge of the electron, J is the current density, and R e is the effective beam radius. In our case, J= 2.02×10 7 A/m 2 , R e =25 nm. Using equ.
(3) and values, we obtained the rise in temperature with respect to the irradiation time. We plotted ΔT e vs t e curve shown in Fig. 3. Figure S11. Calculated curve for rise in temperature of PTO matrix (ΔT e) vs irradiation time (t e ).
Melting temperature of 30 nm size spherical PbTiO 3 nanoparticle is ≈1500 K (where the bulk meting temperature is 1554 K), which was calculated using following equation.
Where, T mp and T mb are the melting temperature of the nanosolid and corresponding bulk material. N/n is a size and shape factor.

Characterization techniques
The High Resolution Transmission Electron Microscopy (HRTEM), X-ray Energy Dispersive Spectroscopy (EDS) analysis and electron irradiations were performed in FEI Tecnai G 2 F30 microscope in which an electron beam produced from the field emission gun, operated at 300 KeV, current density (J) 2.02×10 7 A/m 2 (Electron beam parameters are given in the Table S1 and Fig. S9). The structural dynamic and electron irradiation effect events were recorded on hypercam Gatan CCD camera system with a rate of six frames per second at ambient temperature. The crystalline phases and structures of the materials were characterized with Xray diffraction (XRD) using a Rigaku D/max 2200V/PC diffractometer with Cu Ka radiation (λ = 1.54178 Å). X-ray photoelectron spectroscopy (XPS) using a Thermo Electron Corporation ESCA Lab250 spectrometer at 15kV and 150 W was employed to study the surface characteristic of irradiated and non-irradiated samples.

HRTEM image simulation
HRTEM simulation was carried out using the multislice method using the QSTEM program [2].
The simulated image of Pb particle was calculated from the model which was built on the basis of experimental image. The thickness and defocus values were chosen as 30nm and -34nm, respectively. The sample inclination was not taken into account in simulation.