NOVELTY - The method comprises exposing molecules to a discharge, directing a pulsed supersonic beam (20) of a molecular precursor characterized by kinetic energy of 1 eV per molecule onto a substrate (22) having a temperature of less than 140 degrees C such that non-volatile species of molecules of the precursor are deposited on the substrate, and controlling a number of pulses in the pulsed supersonic beam using a digital controller. The beam is characterized by a pulse duration of less than 50 microseconds, a divergence angle of less than 20 degrees and a pulse rate of 30 Hz, and comprises gas carrier.    USE - The method is useful for fabricating a film, which is useful for a reflective optical element, a solar cell, a transmissive optical element, a birefringent optical element, a polarizing optical element, a semiconductor device, an electronic circuitry and a thin film transistor array (all claimed), where the film is an optical thin film, useful as a blue red reflector coating and as coating for reducing angle-of-incidence dependent spectral response in applications including optical sensors, head mounted display systems, spectacles or sunglasses and useful in laser systems.    ADVANTAGE - The method is capable of rapidly, controllably and accurately fabricating the thin film at low substrate temperature.    DETAILED DESCRIPTION - The method comprises exposing molecules to a discharge, directing a pulsed supersonic beam (20) of a molecular precursor characterized by kinetic energy of 1 eV per molecule onto a substrate (22) having a temperature of less than 140 degrees C such that non-volatile species of molecules of the precursor are deposited on the substrate, and controlling a number of pulses in the pulsed supersonic beam using a digital controller. The beam is characterized by a pulse duration of less than 50 microseconds, a divergence angle of less than 20 degrees and a pulse rate of 30 Hz, and comprises gas carrier. The non-volatile species comprise: collision products, which are produced when the molecules collide with the substrate; and dissociation products, which are produced during the discharge that is carried out by a dielectric barrier-discharge system. The non-volatile species are deposited at a rate of less than 50 atoms in height per pulse. INDEPENDENT CLAIMS are included for:    (1) a film;    (2) a method of generating a beam of atoms or ions; and    (3) a system for generating a beam of atoms or ions.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a system for fabricating a film.    Beam inlet (18)    Pulsed supersonic beam (20)    Substrate (22)    Gas discharge system (26)    Vacuum chamber. (28)