ORA-39170: Schema expression ‘AZAR$RIY’ does not correspond to any schemas

SQL> create user "azar$riy" identified by azar;

User created.

SQL> grant connect,resource,dba to "azar$riy";

Grant succeeded.

SQL> grant read,write on directory data_pump_dir to "azar$riy";

Grant succeeded.

SQL> conn "azar$riy"/azar;
Connected.
SQL> create table a as select * from scott.emp;

Table created.

SQL> commit;

Commit complete.

SQL> exit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

C:\Users\mazar>expdp system/Admin123@azardb directory=data_pump_dir schemas="azar$riy" dumpfile=azartest.dmp log=azartest.log 
Export: Release 11.2.0.1.0 - Production on Sun Nov 7 15:42:09 2010

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORA-39001: invalid argument value
ORA-39170: Schema expression 'AZAR$RIY' does not correspond to any schemas.

C:\Users\mazar>expdp system/Admin123@azardb directory=data_pump_dir schemas='\"azar$riy\"'
 dumpfile=azartest.dmp log=azartest.log 

Export: Release 11.2.0.1.0 - Production on Sun Nov 7 15:42:20 2010

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
Legacy Mode Active due to the following parameters:
Legacy Mode Parameter: "log=azartest.log" Location: Command Line, Replaced with: "logfile=azartest.log"
Legacy Mode has set reuse_dumpfiles=true parameter.
Starting "SYSTEM"."SYS_EXPORT_SCHEMA_01":  system/********@azardb directory=data_pump_dir dumpfile=azartest.dmp logfile=azartest.log schemas='"azar$riy"' reuse
_dumpfiles=true
Estimate in progress using BLOCKS method...
Processing object type SCHEMA_EXPORT/TABLE/TABLE_DATA
Total estimation using BLOCKS method: 64 KB
Processing object type SCHEMA_EXPORT/USER
Processing object type SCHEMA_EXPORT/SYSTEM_GRANT
Processing object type SCHEMA_EXPORT/ROLE_GRANT
Processing object type SCHEMA_EXPORT/DEFAULT_ROLE
Processing object type SCHEMA_EXPORT/PRE_SCHEMA/PROCACT_SCHEMA
Processing object type SCHEMA_EXPORT/TABLE/TABLE
. . exported "azar$riy"."A"                              8.578 KB      14 rows
Master table "SYSTEM"."SYS_EXPORT_SCHEMA_01" successfully loaded/unloaded
******************************************************************************
Dump file set for SYSTEM.SYS_EXPORT_SCHEMA_01 is:
  C:\APP\ORACLE\MAZAR\ADMIN\AZARDB\DPDUMP\AZARTEST.DMP
Job "SYSTEM"."SYS_EXPORT_SCHEMA_01" successfully completed at 15:43:10
C:\Users\mazar>