9 pages. -- PDF file includes: I: Calculation of out-of-plane lattice constants by using Poisson ratio. --II: Additional tables. -- Table S1 Calculated parameters obtained from DFT-based calculations by using a fixed in-plane (3.870 Å) and variable out-of-plane (3.870, 3.906, 3.970 and 3.980 Å) lattice constants of Nb:STO bulk structure. -- Table S2 calculated chemical potential (𝜂) and Seebeck coefficients (S) at 290K from the measured density of charge carriers (n) by using equation (1-4) in the main text for 31 and 11 nm thick Nb:STO films at variable electron band degeneracy (z) and scattering parameter (r). calculations are done by assuming a fixed effective mass of electrons m* (=1.1m0, where m0 is the rest mass of electrons). -- Table S3 Lattice parameters, and calculated band gap of 6%Nb-doped SrTiO3 at the SCAN meta-GGA level. -- Fig. S1. Thickness measurements of the Nb:STO films on LSAT substrates by using x-ray reflectivity and ellipsometry techniques. -- Fig. S2. Schematic illustration of the Seebeck effect measurement on Nb:STO thin films. -- Fig. S3. X-ray diffraction patterns of Nb:STO films deposited on LSAT-001 substrates. -- Fig. S4. Seebeck coefficient measurements of Nb:STO films by two different techniques over a long range of temperature: on-chip Seebeck measurement in a cryostat between 20-300 K and in a LINSEIS instrument within 300-550 K. -- Fig. S5. AFM-topography images of Nb-doped SrTiO3 films on LSAT substrates. -- Fig. S6. Bulk crystal structures of Nb-doped SrTiO3, and unit cells of Nb-doped SrTiO3 films were considered for electronic band structure calculations. -- Fig. S7. Calculated electronic band structures for 4.5, and 8.5 unit cells thick Nb-doped SrTiO3 films. -- Fig. S8 The effective mass calculation by fitting a quadratic function (y=A+Bx+Cx2) at the band edge from the first conduction band as highlighted by the red-line.

Peer reviewed