Integration Services :: Not Able To INSERT Records With MERGE Query

I have a source table #source with columns 'source', 'patientcode' ,'patientdesc'  and it has 4 records as below

source patientcode  patientdesc
canada abc                patient1
canada efg                patient2
canada hij                 patient3
canada klm               patient4

I have a target table and it has 2 records as below.

source prefix  tgt_patientcode  tgt_patientdesc
canada cn         abc patient1
canada cn          efg patient2

Now, I want to merge the source data with target table -that means, if the records are already avaible in target, then ignore and if it does not available then INSERT.

This is the query i used but new records are not getting inserted.

MERGE #target T
USING #source  S
ON S.SOURCE=T.Source 
WHEN NOT MATCHED BY TARGET  THEN
INSERT (  Source, Prefix ,tgt_patientcode ,tgt_patientdesc)
VALUES ('Canada' , 'cn' , s.patientcode, s.patientcode);

I want the output as below

source prefix  tgt_patientcode   tgt_patientdesc 
canada   cn      abc                  patient1
canada cn         efg                   patient2
canada cn        hij               patient3
canada cn         klm patient4

DDL as below :

create table #target (source varchar(100),prefix varchar(2),tgt_patientcode varchar(100),tgt_patientdesc varchar(100))
insert into #target values ('canada','cn','abc','patient1')
insert into #target values ('canada','cn','efg','patient2')

[Code] ....