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We report on our analysis of HST/NICMOS snapshot high resolution images of255 stars in 201 systems within ~10 parsecs of the Sun. Photometry was obtainedthrough filters F110W, F180M, F207M, and F222M using NICMOS Camera 2. Thesefilters were selected to permit clear identification of cool brown dwarfsthrough methane contrast imaging. With a plate scale of 76 mas/pixel, NICMOScan easily resolve binaries with sub-arcsecond separations in the 19".5x19".5field of view. We previously reported five companions to nearby M and L dwarfsfrom this search. No new companions were discovered during the second phase ofdata analysis presented here, confirming that stellar/substellar binaries arerare. We establish magnitude and separation limits for which companions can beruled out for each star in the sample, and then perform a comprehensivesensitivity and completeness analysis for the subsample of 138 M dwarfs in 126systems. We calculate a multiplicity fraction of 0.0{-0.0}^{+3.5}% for Lcompanions to M dwarfs in the separation range of 5 to 70 AU, and2.3_{-0.7}^{+5.0}% for L and T companions to M dwarfs in the separation rangeof 10 to 70 AU. We also discuss trends in the color-magnitude diagrams usingvarious color combinations and present astrometry for 19 multiple systems inour sample. Considering these results and results from several other studies,we argue that the so-called "brown dwarf desert" extends to binary systems withlow mass primaries and is largely independent of primary mass, mass ratio, andseparations. While focusing on companion properties, we discuss how thequalitative agreement between observed companion mass functions and initialmass functions suggests that the paucity of brown dwarfs in either populationmay be due to a common cause and not due to binary formation mechanisms.

The Solar Neighborhood XXVIII: The Multiplicity Fraction of Nearby Stars from 5 to 70 AU and the Brown Dwarf Desert Around M Dwarfs