dir/b > files.txt
I guess it has to be done in PowerShell to preserve unicode signs.
Get-ChildItem | Select-Object -ExpandProperty Name > files.txt
or shorter:
ls | % Name > files.txt
However, you can easily do the same in cmd:
cmd
cmd /u /c "dir /b > files.txt"
The /u switch tells cmd to write things redirected into files as Unicode.
/u