|
Two laser-based methods were used for the deposition of narrow band gap semiconductor films based on iron oxides.
The first one is laser chemical vapor deposition (LCVD) from iron carbonyl Fe(CO)5 vapors using Ar+ laser radiation.
The width of the band gap of the films depends on the film thickness and the applied electrical field. The film thickness
was varied from 10 to 18 nm and consequently the band gap width (Eg) varied from 0.46 to 0.66 eV. The longer the
exposure time of the Si substrate to Ar+ laser radiation, the higher the content of iron oxides, the larger the width of the
band gap in the deposited semiconductor materials. The second method is the reactive pulsed laser deposition (RPLD) of
an iron target in low pressure oxygen atmosphere using a KrF excimer laser (&lgr;=248 nm, &tgr; congruent to 30 ns) at the fluence of 4
J/cm2 and the repetition rate of 10 Hz. A number of pulses (3000-8500) increasing with oxygen ambient pressure (0.05-1
Pa) was used for each deposition with the aim of depositing films with almost equal thickness (~100 nm). The width of
the band gap (Eg) varied in the range 0.13-0.34 eV, depending on the oxygen pressure: the higher the oxygen pressure,
the higher the iron oxide content in the deposited film, the larger the width of the band gap in the deposited
semiconductor material. It is shown that both LCVD and RPLD methods are appropriate technologies for the deposition
of narrow variable band gap semiconductor thin films.
|
