TImestamp with milliseconds or ten thousandths of a second

I am using PostgreSQL to develop an application in .NET where I use a timestamp field. Actually, I am inserting records with the format "yyyy/MM/dd HH:mm:ss". Is it possible to specify milliseconds or ten thounsandths of a second? Is this a PostgreSQL issue or a .NET issue? I guess it is a PostgreSQL issue because the error is generated by the PostgreSQL data provider.

I am trying "yyyy/MM/dd HH:mm:ss.fff" for milliseconds and "yyyy/MM/dd HH:mm:ss.ffff" for ten thousandths of a second but I get an error saying that syntax is not valid.

Respectfully,

Jorge Maldonado