Function Find-User {
  Param ($sam=$(throw "you must enter a sAMAccountname"))
  $searcher=New-Object DirectoryServices.DirectorySearcher
  $searcher.Filter="(&(objectcategory=person)(objectclass=user)(sAMAccountname=$sam))"
  $results=$searcher.FindOne()
  if ($results.path.length -gt 1)
    { 
    write $results
    }
   else
    {
    write "Not Found"
    }
 }

#example
Find-User $env:username