  We present the results of an Halpha near-infrared narrow-band survey
searching for star-forming galaxies at redshift z=0.84. This work is an
extension of our previous narrow-band studies in the optical at lower
redshifts. After removal of stars and redshift interlopers (using spectroscopic
and photometric redshifts), we build a complete sample of 165 Halpha emitters
in the Extended Groth strip and GOODS-N fields with L(Halpha)>10^41 erg/s. We
compute the Halpha luminosity function at z=0.84 after corrections for [NII]
flux contamination, extinction, systematic errors, and incompleteness. Our
sources present an average dust extinction of A(Halpha)=1.5 mag. Adopting
Halpha as a surrogate for the instantaneous star formation rate (SFR), we
measure a extinction-corrected SFR density of 0.17+-0.03 M_sun/yr/Mpc3.
Combining this result to our prior measurements at z=0.02, 0.24, and 0.40, we
derive an Halpha-based evolution of the SFR density proportional to (1+z)^beta
with beta=3.8+-0.5. This evolution is consistent with that derived by other
authors using different SFR tracers.
