Annealing effect on indium tin oxide thin films by DC magnetron sputtering for alkali vapor cell heating

This paper reports the annealing effect on the DC sputter transparent conducting tin-doped indium oxide (ITO) films for the alkali vapor cell heater of the chip-scale atomic sensors. ITO films with a thickness of 140 nm were deposited on BF33 glass substrates at 20 degrees C, followed by an annealing process in N-2 atmosphere for 2 h at different temperatures between 250 degrees C and 500 degrees C. The effect of annealing on the crystal structure, surface morphology, optical, and electrical properties of ITO films was characterized. The predominant orientation of crystal face of the as-deposited and annealed ITO thin films was (222) instead of (400). After annealing at 450 degrees C the ITO film exhibits the highest transmittance (similar to 90%) to the lights at the wavelength of 780 nm, 795 nm and 894 nm regarding the probe light in a chip scale atomic device. Besides, the lowest sheet resistance and resistivity were obtained as 27.8 Omega/square and 3.9 x 10(-4) Omega . cm separately. The refractive index and extinction coefficients results verified the crystal orientation and the transmittance results. This thin ITO film was expected to be the best candidate for the transparent heater in the chip scale atomic devices.