Yes, once you leave the airport you'll need a visa (even if less than 24 hr.) You can purchase this at the immigration desk on arrival with your creditcard. If you don't have a creditcard you can pay cash also (Qatar rial or US dollars) but you'll have to stop by an other desk. The cost for a tourist visa is about $20. However, monitor your Qatar embassy because they were thinking about stopping the visa on arrival program!

I don't know if your employees are eligible but have a look over here: http://www.qatarairways.com/global/en/stop-over.html