Superconducting Tl-Ca-Ba-Cu-0 (TCBCO) thin films about 1 μm thick have been prepared on (100)MgO substrates using a thermal evaporation and improved two-step annealing process involving final thalliation under controlled Tl2O vapour pressure in a quartz reaction tube where the Tl2O vapour pressure was changed by adjusting the position of a Tl2O3-containing boat. The superconducting properties of TCBCO films are strongly dependent on the Tl2O vapour pressure and oxygen partial pressure. Thalliated Tl2Ca1Ba2CuOx, and T12Ca2Ba2Cu3Ox films with Tco's of up to 100 K and Jc,77k's measured over 1 x 0.5 cm^2 area of up to 1 x 10^4 A/cm^2 have been obtained. Preliminary results of prototype step edge dc-SQUID devices are also been described.