Saving a Salesforce Attachment on an android device using ionic

I am trying to save an attachment(an Image) to the device which I retrieve from salesforce using the rest api.

Salesforce returns a binary object which I am trying to save to the android filesystem.

I am using ng-cordova file to create the file and write it to the file system.

I am able to create the file and write in to it, but the written file is corrupt, is there something I need to different before I write the file?

Let me know what you think.

I've attached the code below. 

$.ajax({ // Get the Attachment from saleforce
  url: oauthService.instanceUrl() + data[0].Body,
  type: 'GET',
  headers: {
    'Authorization': 'Bearer' + ' ' + oauthService.accessToken(),
    'Content-type': 'image/png'
  }
}).then(function ok(binaryImage) {
  $cordovaFile.createDir('ExampleDirectory', false).then(function(result) {
    // Directory succesfully Created!

    var replacedString = result.nativeURL;
    replacedString = replacedString.replace('file://', '');

    $cordovaFile.createFile(replacedString + 'test.png', true).then(function(result) {
      // File succesfully created
      $cordovaFile.writeFile(replacedString + 'test.png', binaryImage, {
        'append': false
      }).then(function(result) {
        // Success! image contents succesfully written to file but it does not open succesfully
        alert('file write success : ' + JSON.stringify(result));
      }, function(err) {
        // An error occured. Show a message to the user
        alert('file write error : ' + JSON.stringify(err));
      });
    }, function(err) {
      // An error occured. Show a message to the user
      alert('file create error : ' + JSON.stringify(err));
    });
  }, function(err) {
    // An error occured. Show a message to the user
  });
}, function err(binaryImage) {
  alert('NOT OK ' + JSON.stringify(binaryImage));
});
},
function() {
  //
});