SQL Server : cold backup of master, msdb, model databases

Clear-Host
#  Invoke-Sqlcmd is running the SQL request in Set-Location context.
Set-Location SQLSERVER:\SQL\CHEZNOI\DSFC
[String]$sql="
    SELECT
        physical_name as path
    FROM
        sys.databases AS db
        INNER JOIN sys.master_files AS mf ON db.database_id=mf.database_id
    WHERE
        db.name IN ('master','msdb','model')
"
$files=Invoke-Sqlcmd -Query $sql
#Stop MSSQL Services to do consistent copy of database files
[String]$sqlagent='SQLAgent$DSFC'
[String]$mssql='MSSQL$DSFC'
Stop-Service -Name $sqlagent -Force:$true
Stop-Service -Name $mssql -Force:$true
#Backup database files
[String]$destination='d:\sauve'
$files|Export-Csv -Path "$destination\emplacements.csv" -Force:$true -NoTypeInformation
foreach($file in $files)
{
    Copy-Item -Path ($file).path -Destination $destination -Force:$true
}
#Redémarrage des services
Start-Service -Name $mssql
Start-Service -Name $sqlagent
#Clean PowerShell objects
$file=$null
$files=$null