ionic/Angularjs - not able to unchecked check box on ng-change

I have one drop down and a check box, i want to reset check box value to false whenever drop-down value change. I had already written code for reset check box value to false, but it is not working, please tell me where i am doing wrong.

View:

<label class="item item-input item-select">
        <div class="input-label">Leave Type</div>
        <select ng-model="LeaveRequest.leaveType" ng-change="leavetypechange(LeaveTypes)" required>
          <option value="">Select Leave Type</option>
          <option ng-repeat="lt in LeaveTypes"value="{{lt.Name}} ">{{lt.Name}}</option>
       </select>
</label>
<div ng-show="ShowPeriod">
      <ion-checkbox  ng-model="isChecked" >Half day/ Quarter leave</ion-checkbox>
</div>

controller:

.controller('ApplyLeaveCtrl',function($scope, $state, $templateCache,$ionicPopup) {
 $scope.leavetypechange=function(){ 
            $scope.isChecked=false;
            };
});